diff --git a/Cargo.lock b/Cargo.lock
index 0b44201d56f0b..9a8d9d40b6e45 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4239,6 +4239,7 @@ dependencies = [
  "rustc_hir",
  "rustc_index",
  "rustc_lexer",
+ "rustc_macros",
  "rustc_middle",
  "rustc_serialize",
  "rustc_session",
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 0ceb63477c809..ee96dbc2f60b4 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -7,7 +7,7 @@ use rustc_errors::{
 };
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-use rustc_hir::intravisit::{walk_expr, Visitor};
+use rustc_hir::intravisit::{walk_block, walk_expr, Visitor};
 use rustc_hir::{AsyncGeneratorKind, GeneratorKind};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::ObligationCause;
@@ -23,7 +23,7 @@ use rustc_middle::ty::{
 use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
 use rustc_span::hygiene::DesugaringKind;
 use rustc_span::symbol::sym;
-use rustc_span::{BytePos, Span};
+use rustc_span::{BytePos, Span, Symbol};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::TraitEngineExt as _;
 
@@ -1227,8 +1227,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     from_closure: false,
                     region_name:
                         RegionName {
-                            source:
-                                RegionNameSource::AnonRegionFromUpvar(upvar_span, ref upvar_name),
+                            source: RegionNameSource::AnonRegionFromUpvar(upvar_span, upvar_name),
                             ..
                         },
                     span,
@@ -1500,7 +1499,70 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             | BorrowExplanation::UsedLaterInLoop(..)
             | BorrowExplanation::UsedLaterWhenDropped { .. } => {
                 // Only give this note and suggestion if it could be relevant.
-                err.note("consider using a `let` binding to create a longer lived value");
+                let sm = self.infcx.tcx.sess.source_map();
+                let mut suggested = false;
+                let msg = "consider using a `let` binding to create a longer lived value";
+
+                /// We check that there's a single level of block nesting to ensure always correct
+                /// suggestions. If we don't, then we only provide a free-form message to avoid
+                /// misleading users in cases like `src/test/ui/nll/borrowed-temporary-error.rs`.
+                /// We could expand the analysis to suggest hoising all of the relevant parts of
+                /// the users' code to make the code compile, but that could be too much.
+                struct NestedStatementVisitor {
+                    span: Span,
+                    current: usize,
+                    found: usize,
+                }
+
+                impl<'tcx> Visitor<'tcx> for NestedStatementVisitor {
+                    fn visit_block(&mut self, block: &hir::Block<'tcx>) {
+                        self.current += 1;
+                        walk_block(self, block);
+                        self.current -= 1;
+                    }
+                    fn visit_expr(&mut self, expr: &hir::Expr<'tcx>) {
+                        if self.span == expr.span {
+                            self.found = self.current;
+                        }
+                        walk_expr(self, expr);
+                    }
+                }
+                let source_info = self.body.source_info(location);
+                if let Some(scope) = self.body.source_scopes.get(source_info.scope)
+                    && let ClearCrossCrate::Set(scope_data) = &scope.local_data
+                    && let Some(node) = self.infcx.tcx.hir().find(scope_data.lint_root)
+                    && let Some(id) = node.body_id()
+                    && let hir::ExprKind::Block(block, _) = self.infcx.tcx.hir().body(id).value.kind
+                {
+                    for stmt in block.stmts {
+                        let mut visitor = NestedStatementVisitor {
+                            span: proper_span,
+                            current: 0,
+                            found: 0,
+                        };
+                        visitor.visit_stmt(stmt);
+                        if visitor.found == 0
+                            && stmt.span.contains(proper_span)
+                            && let Some(p) = sm.span_to_margin(stmt.span)
+                            && let Ok(s) = sm.span_to_snippet(proper_span)
+                        {
+                            let addition = format!("let binding = {};\n{}", s, " ".repeat(p));
+                            err.multipart_suggestion_verbose(
+                                msg,
+                                vec![
+                                    (stmt.span.shrink_to_lo(), addition),
+                                    (proper_span, "binding".to_string()),
+                                ],
+                                Applicability::MaybeIncorrect,
+                            );
+                            suggested = true;
+                            break;
+                        }
+                    }
+                }
+                if !suggested {
+                    err.note(msg);
+                }
             }
             _ => {}
         }
@@ -1699,7 +1761,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         borrow_span: Span,
         name: &Option<String>,
         upvar_span: Span,
-        upvar_name: &str,
+        upvar_name: Symbol,
         escape_span: Span,
     ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
         let tcx = self.infcx.tcx;
@@ -2093,7 +2155,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             }
                             StorageDeadOrDrop::Destructor(_) => kind,
                         },
-                        ProjectionElem::Field(..) | ProjectionElem::Downcast(..) => {
+                        ProjectionElem::OpaqueCast { .. }
+                        | ProjectionElem::Field(..)
+                        | ProjectionElem::Downcast(..) => {
                             match place_ty.ty.kind() {
                                 ty::Adt(def, _) if def.has_dtor(tcx) => {
                                     // Report the outermost adt with a destructor
diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 230ccf5199066..72aee0267ac1e 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -12,7 +12,7 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty::adjustment::PointerCast;
 use rustc_middle::ty::{self, RegionVid, TyCtxt};
-use rustc_span::symbol::Symbol;
+use rustc_span::symbol::{kw, Symbol};
 use rustc_span::{sym, DesugaringKind, Span};
 
 use crate::region_infer::BlameConstraint;
@@ -282,7 +282,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
     ) {
         if let ConstraintCategory::OpaqueType = category {
             let suggestable_name =
-                if region_name.was_named() { region_name.to_string() } else { "'_".to_string() };
+                if region_name.was_named() { region_name.name } else { kw::UnderscoreLifetime };
 
             let msg = format!(
                 "you can add a bound to the {}to make it last less than `'static` and match `{}`",
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 53c07a3d481e0..fada3d45fbed8 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -226,6 +226,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 }
                 ProjectionElem::Downcast(..) if including_downcast.0 => return None,
                 ProjectionElem::Downcast(..) => (),
+                ProjectionElem::OpaqueCast(..) => (),
                 ProjectionElem::Field(field, _ty) => {
                     // FIXME(project-rfc_2229#36): print capture precisely here.
                     if let Some(field) = self.is_upvar_field_projection(PlaceRef {
@@ -286,6 +287,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     PlaceRef { local, projection: proj_base }.ty(self.body, self.infcx.tcx)
                 }
                 ProjectionElem::Downcast(..) => place.ty(self.body, self.infcx.tcx),
+                ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(*ty),
                 ProjectionElem::Field(_, field_type) => PlaceTy::from_ty(*field_type),
             },
         };
diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index 8134e1226628f..cb7077fe62171 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -169,6 +169,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                         ..,
                         ProjectionElem::Index(_)
                         | ProjectionElem::ConstantIndex { .. }
+                        | ProjectionElem::OpaqueCast { .. }
                         | ProjectionElem::Subslice { .. }
                         | ProjectionElem::Downcast(..),
                     ],
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 6508c0da75f94..0e6a05478a07e 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -19,8 +19,7 @@ use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::Region;
 use rustc_middle::ty::TypeVisitor;
 use rustc_middle::ty::{self, RegionVid, Ty};
-use rustc_span::symbol::sym;
-use rustc_span::symbol::Ident;
+use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::Span;
 
 use crate::borrowck_errors;
@@ -758,7 +757,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 return;
             };
 
-            let lifetime = if f.has_name() { fr_name.to_string() } else { "'_".to_string() };
+            let lifetime = if f.has_name() { fr_name.name } else { kw::UnderscoreLifetime };
 
             let arg = match param.param.pat.simple_ident() {
                 Some(simple_ident) => format!("argument `{}`", simple_ident),
@@ -770,7 +769,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 self.infcx.tcx,
                 diag,
                 fn_returns,
-                lifetime,
+                lifetime.to_string(),
                 Some(arg),
                 captures,
                 Some((param.param_ty_span, param.param_ty.to_string())),
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index e41af17fbf9b3..4cf1ac4d7abc0 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -34,13 +34,13 @@ pub(crate) enum RegionNameSource {
     /// The `'static` region.
     Static,
     /// The free region corresponding to the environment of a closure.
-    SynthesizedFreeEnvRegion(Span, String),
+    SynthesizedFreeEnvRegion(Span, &'static str),
     /// The region corresponding to an argument.
     AnonRegionFromArgument(RegionNameHighlight),
     /// The region corresponding to a closure upvar.
-    AnonRegionFromUpvar(Span, String),
+    AnonRegionFromUpvar(Span, Symbol),
     /// The region corresponding to the return type of a closure.
-    AnonRegionFromOutput(RegionNameHighlight, String),
+    AnonRegionFromOutput(RegionNameHighlight, &'static str),
     /// The region from a type yielded by a generator.
     AnonRegionFromYieldTy(Span, String),
     /// An anonymous region from an async fn.
@@ -110,7 +110,7 @@ impl RegionName {
             }
             RegionNameSource::SynthesizedFreeEnvRegion(span, note) => {
                 diag.span_label(*span, format!("lifetime `{self}` represents this closure's body"));
-                diag.note(note);
+                diag.note(*note);
             }
             RegionNameSource::AnonRegionFromArgument(RegionNameHighlight::CannotMatchHirTy(
                 span,
@@ -350,10 +350,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
                     Some(RegionName {
                         name: region_name,
-                        source: RegionNameSource::SynthesizedFreeEnvRegion(
-                            fn_decl_span,
-                            note.to_string(),
-                        ),
+                        source: RegionNameSource::SynthesizedFreeEnvRegion(fn_decl_span, note),
                     })
                 }
 
@@ -678,7 +675,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
         Some(RegionName {
             name: region_name,
-            source: RegionNameSource::AnonRegionFromUpvar(upvar_span, upvar_name.to_string()),
+            source: RegionNameSource::AnonRegionFromUpvar(upvar_span, upvar_name),
         })
     }
 
@@ -756,7 +753,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
         Some(RegionName {
             name: self.synthesize_region_name(),
-            source: RegionNameSource::AnonRegionFromOutput(highlight, mir_description.to_string()),
+            source: RegionNameSource::AnonRegionFromOutput(highlight, mir_description),
         })
     }
 
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index e8673ecd3a0b7..74321ddcd9919 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -1788,6 +1788,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         for (place_base, elem) in place.iter_projections().rev() {
             match elem {
                 ProjectionElem::Index(_/*operand*/) |
+                ProjectionElem::OpaqueCast(_) |
                 ProjectionElem::ConstantIndex { .. } |
                 // assigning to P[i] requires P to be valid.
                 ProjectionElem::Downcast(_/*adt_def*/, _/*variant_idx*/) =>
@@ -2179,6 +2180,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     | ProjectionElem::Index(..)
                     | ProjectionElem::ConstantIndex { .. }
                     | ProjectionElem::Subslice { .. }
+                    | ProjectionElem::OpaqueCast { .. }
                     | ProjectionElem::Downcast(..) => {
                         let upvar_field_projection = self.is_upvar_field_projection(place);
                         if let Some(field) = upvar_field_projection {
diff --git a/compiler/rustc_borrowck/src/places_conflict.rs b/compiler/rustc_borrowck/src/places_conflict.rs
index 97335fd0dffae..5b67e6aa1cffa 100644
--- a/compiler/rustc_borrowck/src/places_conflict.rs
+++ b/compiler/rustc_borrowck/src/places_conflict.rs
@@ -255,6 +255,7 @@ fn place_components_conflict<'tcx>(
                 | (ProjectionElem::Index { .. }, _, _)
                 | (ProjectionElem::ConstantIndex { .. }, _, _)
                 | (ProjectionElem::Subslice { .. }, _, _)
+                | (ProjectionElem::OpaqueCast { .. }, _, _)
                 | (ProjectionElem::Downcast { .. }, _, _) => {
                     // Recursive case. This can still be disjoint on a
                     // further iteration if this a shallow access and
@@ -322,6 +323,17 @@ fn place_projection_conflict<'tcx>(
             debug!("place_element_conflict: DISJOINT-OR-EQ-DEREF");
             Overlap::EqualOrDisjoint
         }
+        (ProjectionElem::OpaqueCast(v1), ProjectionElem::OpaqueCast(v2)) => {
+            if v1 == v2 {
+                // same type - recur.
+                debug!("place_element_conflict: DISJOINT-OR-EQ-OPAQUE");
+                Overlap::EqualOrDisjoint
+            } else {
+                // Different types. Disjoint!
+                debug!("place_element_conflict: DISJOINT-OPAQUE");
+                Overlap::Disjoint
+            }
+        }
         (ProjectionElem::Field(f1, _), ProjectionElem::Field(f2, _)) => {
             if f1 == f2 {
                 // same field (e.g., `a.y` vs. `a.y`) - recur.
@@ -525,6 +537,7 @@ fn place_projection_conflict<'tcx>(
             | ProjectionElem::Field(..)
             | ProjectionElem::Index(..)
             | ProjectionElem::ConstantIndex { .. }
+            | ProjectionElem::OpaqueCast { .. }
             | ProjectionElem::Subslice { .. }
             | ProjectionElem::Downcast(..),
             _,
diff --git a/compiler/rustc_borrowck/src/prefixes.rs b/compiler/rustc_borrowck/src/prefixes.rs
index bdf2becb71126..2b50cbac9a02d 100644
--- a/compiler/rustc_borrowck/src/prefixes.rs
+++ b/compiler/rustc_borrowck/src/prefixes.rs
@@ -81,6 +81,7 @@ impl<'cx, 'tcx> Iterator for Prefixes<'cx, 'tcx> {
                         }
                         ProjectionElem::Downcast(..)
                         | ProjectionElem::Subslice { .. }
+                        | ProjectionElem::OpaqueCast { .. }
                         | ProjectionElem::ConstantIndex { .. }
                         | ProjectionElem::Index(_) => {
                             cursor = cursor_base;
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index cf2140097e6da..8e763a02af33f 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -790,6 +790,19 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
                 }
                 PlaceTy::from_ty(fty)
             }
+            ProjectionElem::OpaqueCast(ty) => {
+                let ty = self.sanitize_type(place, ty);
+                let ty = self.cx.normalize(ty, location);
+                self.cx
+                    .eq_types(
+                        base.ty,
+                        ty,
+                        location.to_locations(),
+                        ConstraintCategory::TypeAnnotation,
+                    )
+                    .unwrap();
+                PlaceTy::from_ty(ty)
+            }
         }
     }
 
@@ -1195,10 +1208,11 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 tcx,
                 self.param_env,
                 proj,
-                |this, field, ()| {
+                |this, field, _| {
                     let ty = this.field_ty(tcx, field);
                     self.normalize(ty, locations)
                 },
+                |_, _| unreachable!(),
             );
             curr_projected_ty = projected_ty;
         }
@@ -2493,6 +2507,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 }
                 ProjectionElem::Field(..)
                 | ProjectionElem::Downcast(..)
+                | ProjectionElem::OpaqueCast(..)
                 | ProjectionElem::Index(..)
                 | ProjectionElem::ConstantIndex { .. }
                 | ProjectionElem::Subslice { .. } => {
diff --git a/compiler/rustc_codegen_cranelift/src/base.rs b/compiler/rustc_codegen_cranelift/src/base.rs
index 63cd4d6de4c3e..54652623d9401 100644
--- a/compiler/rustc_codegen_cranelift/src/base.rs
+++ b/compiler/rustc_codegen_cranelift/src/base.rs
@@ -825,6 +825,7 @@ pub(crate) fn codegen_place<'tcx>(
                     cplace = cplace.place_deref(fx);
                 }
             }
+            PlaceElem::OpaqueCast(ty) => cplace = cplace.place_opaque_cast(fx, ty),
             PlaceElem::Field(field, _ty) => {
                 cplace = cplace.place_field(fx, field);
             }
diff --git a/compiler/rustc_codegen_cranelift/src/value_and_place.rs b/compiler/rustc_codegen_cranelift/src/value_and_place.rs
index a68225de58b32..8ff35d2f76dbf 100644
--- a/compiler/rustc_codegen_cranelift/src/value_and_place.rs
+++ b/compiler/rustc_codegen_cranelift/src/value_and_place.rs
@@ -615,6 +615,14 @@ impl<'tcx> CPlace<'tcx> {
         }
     }
 
+    pub(crate) fn place_opaque_cast(
+        self,
+        fx: &mut FunctionCx<'_, '_, 'tcx>,
+        ty: Ty<'tcx>,
+    ) -> CPlace<'tcx> {
+        CPlace { inner: self.inner, layout: fx.layout_of(ty) }
+    }
+
     pub(crate) fn place_field(
         self,
         fx: &mut FunctionCx<'_, '_, 'tcx>,
diff --git a/compiler/rustc_codegen_ssa/src/mir/place.rs b/compiler/rustc_codegen_ssa/src/mir/place.rs
index 58cee0c8bb0db..421d6f807ae8e 100644
--- a/compiler/rustc_codegen_ssa/src/mir/place.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/place.rs
@@ -411,6 +411,21 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
         downcast
     }
 
+    pub fn project_type<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
+        &self,
+        bx: &mut Bx,
+        ty: Ty<'tcx>,
+    ) -> Self {
+        let mut downcast = *self;
+        downcast.layout = bx.cx().layout_of(ty);
+
+        // Cast to the appropriate type.
+        let variant_ty = bx.cx().backend_type(downcast.layout);
+        downcast.llval = bx.pointercast(downcast.llval, bx.cx().type_ptr_to(variant_ty));
+
+        downcast
+    }
+
     pub fn storage_live<Bx: BuilderMethods<'a, 'tcx, Value = V>>(&self, bx: &mut Bx) {
         bx.lifetime_start(self.llval, self.layout.size);
     }
@@ -459,6 +474,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 mir::ProjectionElem::Field(ref field, _) => {
                     cg_base.project_field(bx, field.index())
                 }
+                mir::ProjectionElem::OpaqueCast(ty) => cg_base.project_type(bx, ty),
                 mir::ProjectionElem::Index(index) => {
                     let index = &mir::Operand::Copy(mir::Place::from(index));
                     let index = self.codegen_operand(bx, index);
diff --git a/compiler/rustc_const_eval/src/const_eval/valtrees.rs b/compiler/rustc_const_eval/src/const_eval/valtrees.rs
index 2288a4e7b6c78..8fff4571d127c 100644
--- a/compiler/rustc_const_eval/src/const_eval/valtrees.rs
+++ b/compiler/rustc_const_eval/src/const_eval/valtrees.rs
@@ -436,7 +436,7 @@ fn valtree_into_mplace<'tcx>(
 
                         let offset = place_adjusted.layout.fields.offset(i);
                         place
-                            .offset(
+                            .offset_with_meta(
                                 offset,
                                 MemPlaceMeta::Meta(Scalar::from_machine_usize(
                                     num_elems as u64,
diff --git a/compiler/rustc_const_eval/src/interpret/operand.rs b/compiler/rustc_const_eval/src/interpret/operand.rs
index 1465b98629345..22dc1e80f13a8 100644
--- a/compiler/rustc_const_eval/src/interpret/operand.rs
+++ b/compiler/rustc_const_eval/src/interpret/operand.rs
@@ -297,7 +297,7 @@ impl<'tcx, Tag: Provenance> OpTy<'tcx, Tag> {
         }
     }
 
-    pub fn offset(
+    pub fn offset_with_meta(
         &self,
         offset: Size,
         meta: MemPlaceMeta<Tag>,
@@ -305,7 +305,7 @@ impl<'tcx, Tag: Provenance> OpTy<'tcx, Tag> {
         cx: &impl HasDataLayout,
     ) -> InterpResult<'tcx, Self> {
         match self.try_as_mplace() {
-            Ok(mplace) => Ok(mplace.offset(offset, meta, layout, cx)?.into()),
+            Ok(mplace) => Ok(mplace.offset_with_meta(offset, meta, layout, cx)?.into()),
             Err(imm) => {
                 assert!(
                     matches!(*imm, Immediate::Uninit),
@@ -317,6 +317,16 @@ impl<'tcx, Tag: Provenance> OpTy<'tcx, Tag> {
             }
         }
     }
+
+    pub fn offset(
+        &self,
+        offset: Size,
+        layout: TyAndLayout<'tcx>,
+        cx: &impl HasDataLayout,
+    ) -> InterpResult<'tcx, Self> {
+        assert!(!layout.is_unsized());
+        self.offset_with_meta(offset, MemPlaceMeta::None, layout, cx)
+    }
 }
 
 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs
index f4b11ea196757..a29a1492c8ef3 100644
--- a/compiler/rustc_const_eval/src/interpret/place.rs
+++ b/compiler/rustc_const_eval/src/interpret/place.rs
@@ -163,7 +163,7 @@ impl<Tag: Provenance> MemPlace<Tag> {
     }
 
     #[inline]
-    pub fn offset<'tcx>(
+    pub fn offset_with_meta<'tcx>(
         self,
         offset: Size,
         meta: MemPlaceMeta<Tag>,
@@ -199,7 +199,7 @@ impl<'tcx, Tag: Provenance> MPlaceTy<'tcx, Tag> {
     }
 
     #[inline]
-    pub fn offset(
+    pub fn offset_with_meta(
         &self,
         offset: Size,
         meta: MemPlaceMeta<Tag>,
@@ -207,12 +207,22 @@ impl<'tcx, Tag: Provenance> MPlaceTy<'tcx, Tag> {
         cx: &impl HasDataLayout,
     ) -> InterpResult<'tcx, Self> {
         Ok(MPlaceTy {
-            mplace: self.mplace.offset(offset, meta, cx)?,
+            mplace: self.mplace.offset_with_meta(offset, meta, cx)?,
             align: self.align.restrict_for_offset(offset),
             layout,
         })
     }
 
+    pub fn offset(
+        &self,
+        offset: Size,
+        layout: TyAndLayout<'tcx>,
+        cx: &impl HasDataLayout,
+    ) -> InterpResult<'tcx, Self> {
+        assert!(!layout.is_unsized());
+        self.offset_with_meta(offset, MemPlaceMeta::None, layout, cx)
+    }
+
     #[inline]
     pub fn from_aligned_ptr(ptr: Pointer<Option<Tag>>, layout: TyAndLayout<'tcx>) -> Self {
         MPlaceTy { mplace: MemPlace::from_ptr(ptr), layout, align: layout.align.abi }
diff --git a/compiler/rustc_const_eval/src/interpret/projection.rs b/compiler/rustc_const_eval/src/interpret/projection.rs
index 31fb6a8944df6..704dc6db06071 100644
--- a/compiler/rustc_const_eval/src/interpret/projection.rs
+++ b/compiler/rustc_const_eval/src/interpret/projection.rs
@@ -63,7 +63,7 @@ where
 
         // We do not look at `base.layout.align` nor `field_layout.align`, unlike
         // codegen -- mostly to see if we can get away with that
-        base.offset(offset, meta, field_layout, self)
+        base.offset_with_meta(offset, meta, field_layout, self)
     }
 
     /// Gets the place of a field inside the place, and also the field's type.
@@ -193,9 +193,7 @@ where
                 let offset = stride * index; // `Size` multiplication
                 // All fields have the same layout.
                 let field_layout = base.layout.field(self, 0);
-                assert!(!field_layout.is_unsized());
-
-                base.offset(offset, MemPlaceMeta::None, field_layout, self)
+                base.offset(offset, field_layout, self)
             }
             _ => span_bug!(
                 self.cur_span(),
@@ -215,10 +213,10 @@ where
         let abi::FieldsShape::Array { stride, .. } = base.layout.fields else {
             span_bug!(self.cur_span(), "operand_array_fields: expected an array layout");
         };
-        let layout = base.layout.field(self, 0);
+        let field_layout = base.layout.field(self, 0);
         let dl = &self.tcx.data_layout;
         // `Size` multiplication
-        Ok((0..len).map(move |i| base.offset(stride * i, MemPlaceMeta::None, layout, dl)))
+        Ok((0..len).map(move |i| base.offset(stride * i, field_layout, dl)))
     }
 
     /// Index into an array.
@@ -326,7 +324,7 @@ where
             }
         };
         let layout = self.layout_of(ty)?;
-        base.offset(from_offset, meta, layout, self)
+        base.offset_with_meta(from_offset, meta, layout, self)
     }
 
     pub fn place_subslice(
@@ -351,6 +349,11 @@ where
     ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
         use rustc_middle::mir::ProjectionElem::*;
         Ok(match proj_elem {
+            OpaqueCast(ty) => {
+                let mut place = *base;
+                place.layout = self.layout_of(ty)?;
+                place
+            }
             Field(field, _) => self.place_field(base, field.index())?,
             Downcast(_, variant) => self.place_downcast(base, variant)?,
             Deref => self.deref_operand(&self.place_to_op(base)?)?.into(),
@@ -375,6 +378,11 @@ where
     ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
         use rustc_middle::mir::ProjectionElem::*;
         Ok(match proj_elem {
+            OpaqueCast(ty) => {
+                let mut op = *base;
+                op.layout = self.layout_of(ty)?;
+                op
+            }
             Field(field, _) => self.operand_field(base, field.index())?,
             Downcast(_, variant) => self.operand_downcast(base, variant)?,
             Deref => self.deref_operand(base)?.into(),
diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index 53bc2cc8a6980..2e5492ecf5601 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -853,7 +853,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
                 self.visit_scalar(scalar, scalar_layout)?;
             }
             Abi::ScalarPair(a_layout, b_layout) => {
-                // We would validate these things as we descend into the fields,
+                // There is no `rustc_layout_scalar_valid_range_start` for pairs, so
+                // we would validate these things as we descend into the fields,
                 // but that can miss bugs in layout computation. Layout computation
                 // is subtle due to enums having ScalarPair layout, where one field
                 // is the discriminant.
@@ -867,7 +868,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
             }
             Abi::Vector { .. } => {
                 // No checks here, we assume layout computation gets this right.
-                // (This is harder to check since Miri does not represent these as `Immediate`.)
+                // (This is harder to check since Miri does not represent these as `Immediate`. We
+                // also cannot use field projections since this might be a newtype around a vector.)
             }
             Abi::Aggregate { .. } => {
                 // Nothing to do.
diff --git a/compiler/rustc_const_eval/src/interpret/visitor.rs b/compiler/rustc_const_eval/src/interpret/visitor.rs
index c262bca9bb4ee..f6a0c19d25953 100644
--- a/compiler/rustc_const_eval/src/interpret/visitor.rs
+++ b/compiler/rustc_const_eval/src/interpret/visitor.rs
@@ -8,23 +8,33 @@ use rustc_target::abi::{FieldsShape, VariantIdx, Variants};
 
 use std::num::NonZeroUsize;
 
-use super::{InterpCx, MPlaceTy, Machine, OpTy};
+use super::{InterpCx, MPlaceTy, Machine, OpTy, PlaceTy};
 
-// A thing that we can project into, and that has a layout.
-// This wouldn't have to depend on `Machine` but with the current type inference,
-// that's just more convenient to work with (avoids repeating all the `Machine` bounds).
+/// A thing that we can project into, and that has a layout.
+/// This wouldn't have to depend on `Machine` but with the current type inference,
+/// that's just more convenient to work with (avoids repeating all the `Machine` bounds).
 pub trait Value<'mir, 'tcx, M: Machine<'mir, 'tcx>>: Copy {
     /// Gets this value's layout.
     fn layout(&self) -> TyAndLayout<'tcx>;
 
-    /// Makes this into an `OpTy`.
-    fn to_op(&self, ecx: &InterpCx<'mir, 'tcx, M>)
-    -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>>;
+    /// Makes this into an `OpTy`, in a cheap way that is good for reading.
+    fn to_op_for_read(
+        &self,
+        ecx: &InterpCx<'mir, 'tcx, M>,
+    ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>>;
+
+    /// Makes this into an `OpTy`, in a potentially more expensive way that is good for projections.
+    fn to_op_for_proj(
+        &self,
+        ecx: &InterpCx<'mir, 'tcx, M>,
+    ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
+        self.to_op_for_read(ecx)
+    }
 
     /// Creates this from an `OpTy`.
     ///
-    /// If `to_op` only ever produces `Indirect` operands, then this one is definitely `Indirect`.
-    fn from_op(mplace: OpTy<'tcx, M::PointerTag>) -> Self;
+    /// If `to_op_for_proj` only ever produces `Indirect` operands, then this one is definitely `Indirect`.
+    fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self;
 
     /// Projects to the given enum variant.
     fn project_downcast(
@@ -41,8 +51,50 @@ pub trait Value<'mir, 'tcx, M: Machine<'mir, 'tcx>>: Copy {
     ) -> InterpResult<'tcx, Self>;
 }
 
-// Operands and memory-places are both values.
-// Places in general are not due to `place_field` having to do `force_allocation`.
+/// A thing that we can project into given *mutable* access to `ecx`, and that has a layout.
+/// This wouldn't have to depend on `Machine` but with the current type inference,
+/// that's just more convenient to work with (avoids repeating all the `Machine` bounds).
+pub trait ValueMut<'mir, 'tcx, M: Machine<'mir, 'tcx>>: Copy {
+    /// Gets this value's layout.
+    fn layout(&self) -> TyAndLayout<'tcx>;
+
+    /// Makes this into an `OpTy`, in a cheap way that is good for reading.
+    fn to_op_for_read(
+        &self,
+        ecx: &InterpCx<'mir, 'tcx, M>,
+    ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>>;
+
+    /// Makes this into an `OpTy`, in a potentially more expensive way that is good for projections.
+    fn to_op_for_proj(
+        &self,
+        ecx: &mut InterpCx<'mir, 'tcx, M>,
+    ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>>;
+
+    /// Creates this from an `OpTy`.
+    ///
+    /// If `to_op_for_proj` only ever produces `Indirect` operands, then this one is definitely `Indirect`.
+    fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self;
+
+    /// Projects to the given enum variant.
+    fn project_downcast(
+        &self,
+        ecx: &mut InterpCx<'mir, 'tcx, M>,
+        variant: VariantIdx,
+    ) -> InterpResult<'tcx, Self>;
+
+    /// Projects to the n-th field.
+    fn project_field(
+        &self,
+        ecx: &mut InterpCx<'mir, 'tcx, M>,
+        field: usize,
+    ) -> InterpResult<'tcx, Self>;
+}
+
+// We cannot have a general impl which shows that Value implies ValueMut. (When we do, it says we
+// cannot `impl ValueMut for PlaceTy` because some downstream crate could `impl Value for PlaceTy`.)
+// So we have some copy-paste here. (We could have a macro but since we only have 2 types with this
+// double-impl, that would barely make the code shorter, if at all.)
+
 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M> for OpTy<'tcx, M::PointerTag> {
     #[inline(always)]
     fn layout(&self) -> TyAndLayout<'tcx> {
@@ -50,7 +102,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M> for OpTy<'tc
     }
 
     #[inline(always)]
-    fn to_op(
+    fn to_op_for_read(
         &self,
         _ecx: &InterpCx<'mir, 'tcx, M>,
     ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
@@ -58,8 +110,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M> for OpTy<'tc
     }
 
     #[inline(always)]
-    fn from_op(op: OpTy<'tcx, M::PointerTag>) -> Self {
-        op
+    fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self {
+        *op
     }
 
     #[inline(always)]
@@ -81,6 +133,54 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M> for OpTy<'tc
     }
 }
 
+impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueMut<'mir, 'tcx, M>
+    for OpTy<'tcx, M::PointerTag>
+{
+    #[inline(always)]
+    fn layout(&self) -> TyAndLayout<'tcx> {
+        self.layout
+    }
+
+    #[inline(always)]
+    fn to_op_for_read(
+        &self,
+        _ecx: &InterpCx<'mir, 'tcx, M>,
+    ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
+        Ok(*self)
+    }
+
+    #[inline(always)]
+    fn to_op_for_proj(
+        &self,
+        _ecx: &mut InterpCx<'mir, 'tcx, M>,
+    ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
+        Ok(*self)
+    }
+
+    #[inline(always)]
+    fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self {
+        *op
+    }
+
+    #[inline(always)]
+    fn project_downcast(
+        &self,
+        ecx: &mut InterpCx<'mir, 'tcx, M>,
+        variant: VariantIdx,
+    ) -> InterpResult<'tcx, Self> {
+        ecx.operand_downcast(self, variant)
+    }
+
+    #[inline(always)]
+    fn project_field(
+        &self,
+        ecx: &mut InterpCx<'mir, 'tcx, M>,
+        field: usize,
+    ) -> InterpResult<'tcx, Self> {
+        ecx.operand_field(self, field)
+    }
+}
+
 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M>
     for MPlaceTy<'tcx, M::PointerTag>
 {
@@ -90,7 +190,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M>
     }
 
     #[inline(always)]
-    fn to_op(
+    fn to_op_for_read(
         &self,
         _ecx: &InterpCx<'mir, 'tcx, M>,
     ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
@@ -98,8 +198,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M>
     }
 
     #[inline(always)]
-    fn from_op(op: OpTy<'tcx, M::PointerTag>) -> Self {
-        // assert is justified because our `to_op` only ever produces `Indirect` operands.
+    fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self {
+        // assert is justified because our `to_op_for_read` only ever produces `Indirect` operands.
         op.assert_mem_place()
     }
 
@@ -122,11 +222,111 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M>
     }
 }
 
+impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueMut<'mir, 'tcx, M>
+    for MPlaceTy<'tcx, M::PointerTag>
+{
+    #[inline(always)]
+    fn layout(&self) -> TyAndLayout<'tcx> {
+        self.layout
+    }
+
+    #[inline(always)]
+    fn to_op_for_read(
+        &self,
+        _ecx: &InterpCx<'mir, 'tcx, M>,
+    ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
+        Ok(self.into())
+    }
+
+    #[inline(always)]
+    fn to_op_for_proj(
+        &self,
+        _ecx: &mut InterpCx<'mir, 'tcx, M>,
+    ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
+        Ok(self.into())
+    }
+
+    #[inline(always)]
+    fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self {
+        // assert is justified because our `to_op_for_proj` only ever produces `Indirect` operands.
+        op.assert_mem_place()
+    }
+
+    #[inline(always)]
+    fn project_downcast(
+        &self,
+        ecx: &mut InterpCx<'mir, 'tcx, M>,
+        variant: VariantIdx,
+    ) -> InterpResult<'tcx, Self> {
+        ecx.mplace_downcast(self, variant)
+    }
+
+    #[inline(always)]
+    fn project_field(
+        &self,
+        ecx: &mut InterpCx<'mir, 'tcx, M>,
+        field: usize,
+    ) -> InterpResult<'tcx, Self> {
+        ecx.mplace_field(self, field)
+    }
+}
+
+impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueMut<'mir, 'tcx, M>
+    for PlaceTy<'tcx, M::PointerTag>
+{
+    #[inline(always)]
+    fn layout(&self) -> TyAndLayout<'tcx> {
+        self.layout
+    }
+
+    #[inline(always)]
+    fn to_op_for_read(
+        &self,
+        ecx: &InterpCx<'mir, 'tcx, M>,
+    ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
+        // We `force_allocation` here so that `from_op` below can work.
+        ecx.place_to_op(self)
+    }
+
+    #[inline(always)]
+    fn to_op_for_proj(
+        &self,
+        ecx: &mut InterpCx<'mir, 'tcx, M>,
+    ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
+        // We `force_allocation` here so that `from_op` below can work.
+        Ok(ecx.force_allocation(self)?.into())
+    }
+
+    #[inline(always)]
+    fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self {
+        // assert is justified because our `to_op` only ever produces `Indirect` operands.
+        op.assert_mem_place().into()
+    }
+
+    #[inline(always)]
+    fn project_downcast(
+        &self,
+        ecx: &mut InterpCx<'mir, 'tcx, M>,
+        variant: VariantIdx,
+    ) -> InterpResult<'tcx, Self> {
+        ecx.place_downcast(self, variant)
+    }
+
+    #[inline(always)]
+    fn project_field(
+        &self,
+        ecx: &mut InterpCx<'mir, 'tcx, M>,
+        field: usize,
+    ) -> InterpResult<'tcx, Self> {
+        ecx.place_field(self, field)
+    }
+}
+
 macro_rules! make_value_visitor {
-    ($visitor_trait_name:ident, $($mutability:ident)?) => {
+    ($visitor_trait:ident, $value_trait:ident, $($mutability:ident)?) => {
         // How to traverse a value and what to do when we are at the leaves.
-        pub trait $visitor_trait_name<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>: Sized {
-            type V: Value<'mir, 'tcx, M>;
+        pub trait $visitor_trait<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>: Sized {
+            type V: $value_trait<'mir, 'tcx, M>;
 
             /// The visitor must have an `InterpCx` in it.
             fn ecx(&$($mutability)? self)
@@ -215,19 +415,20 @@ macro_rules! make_value_visitor {
             }
             fn walk_value(&mut self, v: &Self::V) -> InterpResult<'tcx>
             {
-                trace!("walk_value: type: {}", v.layout().ty);
+                let ty = v.layout().ty;
+                trace!("walk_value: type: {ty}");
 
                 // Special treatment for special types, where the (static) layout is not sufficient.
-                match *v.layout().ty.kind() {
+                match *ty.kind() {
                     // If it is a trait object, switch to the real type that was used to create it.
                     ty::Dynamic(..) => {
                         // unsized values are never immediate, so we can assert_mem_place
-                        let op = v.to_op(self.ecx())?;
+                        let op = v.to_op_for_read(self.ecx())?;
                         let dest = op.assert_mem_place();
-                        let inner = self.ecx().unpack_dyn_trait(&dest)?.1;
-                        trace!("walk_value: dyn object layout: {:#?}", inner.layout);
+                        let inner_mplace = self.ecx().unpack_dyn_trait(&dest)?.1;
+                        trace!("walk_value: dyn object layout: {:#?}", inner_mplace.layout);
                         // recurse with the inner type
-                        return self.visit_field(&v, 0, &Value::from_op(inner.into()));
+                        return self.visit_field(&v, 0, &$value_trait::from_op(&inner_mplace.into()));
                     },
                     // Slices do not need special handling here: they have `Array` field
                     // placement with length 0, so we enter the `Array` case below which
@@ -278,10 +479,10 @@ macro_rules! make_value_visitor {
 
                 // Visit the fields of this value.
                 match v.layout().fields {
-                    FieldsShape::Primitive => {},
+                    FieldsShape::Primitive => {}
                     FieldsShape::Union(fields) => {
                         self.visit_union(v, fields)?;
-                    },
+                    }
                     FieldsShape::Arbitrary { ref offsets, .. } => {
                         // FIXME: We collect in a vec because otherwise there are lifetime
                         // errors: Projecting to a field needs access to `ecx`.
@@ -291,16 +492,17 @@ macro_rules! make_value_visitor {
                             })
                             .collect();
                         self.visit_aggregate(v, fields.into_iter())?;
-                    },
+                    }
                     FieldsShape::Array { .. } => {
-                        // Let's get an mplace first.
-                        let op = v.to_op(self.ecx())?;
+                        // Let's get an mplace (or immediate) first.
+                        // This might `force_allocate` if `v` is a `PlaceTy`, but `place_index` does that anyway.
+                        let op = v.to_op_for_proj(self.ecx())?;
                         // Now we can go over all the fields.
                         // This uses the *run-time length*, i.e., if we are a slice,
                         // the dynamic info from the metadata is used.
                         let iter = self.ecx().operand_array_fields(&op)?
                             .map(|f| f.and_then(|f| {
-                                Ok(Value::from_op(f))
+                                Ok($value_trait::from_op(&f))
                             }));
                         self.visit_aggregate(v, iter)?;
                     }
@@ -310,7 +512,7 @@ macro_rules! make_value_visitor {
                     // If this is a multi-variant layout, find the right variant and proceed
                     // with *its* fields.
                     Variants::Multiple { .. } => {
-                        let op = v.to_op(self.ecx())?;
+                        let op = v.to_op_for_read(self.ecx())?;
                         let idx = self.read_discriminant(&op)?;
                         let inner = v.project_downcast(self.ecx(), idx)?;
                         trace!("walk_value: variant layout: {:#?}", inner.layout());
@@ -325,5 +527,5 @@ macro_rules! make_value_visitor {
     }
 }
 
-make_value_visitor!(ValueVisitor,);
-make_value_visitor!(MutValueVisitor, mut);
+make_value_visitor!(ValueVisitor, Value,);
+make_value_visitor!(MutValueVisitor, ValueMut, mut);
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/check.rs b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
index 628298df47385..0581f4919782d 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
@@ -652,6 +652,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
             ProjectionElem::ConstantIndex { .. }
             | ProjectionElem::Downcast(..)
+            | ProjectionElem::OpaqueCast(..)
             | ProjectionElem::Subslice { .. }
             | ProjectionElem::Field(..)
             | ProjectionElem::Index(_) => {}
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs b/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
index 29464cf8c4e4f..c2b4f6eca5ced 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
@@ -316,6 +316,7 @@ where
 
             ProjectionElem::Deref
             | ProjectionElem::Field(_, _)
+            | ProjectionElem::OpaqueCast(_)
             | ProjectionElem::ConstantIndex { .. }
             | ProjectionElem::Subslice { .. }
             | ProjectionElem::Downcast(_, _)
diff --git a/compiler/rustc_const_eval/src/transform/promote_consts.rs b/compiler/rustc_const_eval/src/transform/promote_consts.rs
index ed4d8c95d1e61..daa154576ae4b 100644
--- a/compiler/rustc_const_eval/src/transform/promote_consts.rs
+++ b/compiler/rustc_const_eval/src/transform/promote_consts.rs
@@ -361,7 +361,7 @@ impl<'tcx> Validator<'_, 'tcx> {
                             return Err(Unpromotable);
                         }
                     }
-                    ProjectionElem::Downcast(..) => {
+                    ProjectionElem::OpaqueCast(..) | ProjectionElem::Downcast(..) => {
                         return Err(Unpromotable);
                     }
 
diff --git a/compiler/rustc_error_messages/locales/en-US/passes.ftl b/compiler/rustc_error_messages/locales/en-US/passes.ftl
new file mode 100644
index 0000000000000..e4c9a4dad7b48
--- /dev/null
+++ b/compiler/rustc_error_messages/locales/en-US/passes.ftl
@@ -0,0 +1,151 @@
+-passes-previously-accepted =
+    this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+
+-passes-see-issue =
+    see issue #{$issue} <https://github.com/rust-lang/rust/issues/{$issue}> for more information
+
+passes-outer-crate-level-attr =
+    crate-level attribute should be an inner attribute: add an exclamation mark: `#![foo]`
+
+passes-inner-crate-level-attr =
+    crate-level attribute should be in the root module
+
+passes-ignored-attr-with-macro = `#[{$sym}]` is ignored on struct fields, match arms and macro defs
+    .warn = {-passes-previously-accepted}
+    .note = {-passes-see-issue(issue: "80564")}
+
+passes-ignored-attr = `#[{$sym}]` is ignored on struct fields and match arms
+    .warn = {-passes-previously-accepted}
+    .note = {-passes-see-issue(issue: "80564")}
+
+passes-inline-ignored-function-prototype = `#[inline]` is ignored on function prototypes
+
+passes-inline-ignored-constants = `#[inline]` is ignored on constants
+    .warn = {-passes-previously-accepted}
+    .note = {-passes-see-issue(issue: "65833")}
+
+passes-inline-not-fn-or-closure = attribute should be applied to function or closure
+    .label = not a function or closure
+
+passes-no-coverage-ignored-function-prototype = `#[no_coverage]` is ignored on function prototypes
+
+passes-no-coverage-propagate =
+    `#[no_coverage]` does not propagate into items and must be applied to the contained functions directly
+
+passes-no-coverage-fn-defn = `#[no_coverage]` may only be applied to function definitions
+
+passes-no-coverage-not-coverable = `#[no_coverage]` must be applied to coverable code
+    .label = not coverable code
+
+passes-should-be-applied-to-fn = attribute should be applied to a function definition
+    .label = not a function definition
+
+passes-naked-tracked-caller = cannot use `#[track_caller]` with `#[naked]`
+
+passes-should-be-applied-to-struct-enum = attribute should be applied to a struct or enum
+    .label = not a struct or enum
+
+passes-should-be-applied-to-trait = attribute should be applied to a trait
+    .label = not a trait
+
+passes-target-feature-on-statement = {passes-should-be-applied-to-fn}
+    .warn = {-passes-previously-accepted}
+    .label = {passes-should-be-applied-to-fn.label}
+
+passes-should-be-applied-to-static = attribute should be applied to a static
+    .label = not a static
+
+passes-doc-expect-str = doc {$attr_name} attribute expects a string: #[doc({$attr_name} = "a")]
+
+passes-doc-alias-empty = {$attr_str} attribute cannot have empty value
+
+passes-doc-alias-bad-char = {$char_} character isn't allowed in {$attr_str}
+
+passes-doc-alias-start-end = {$attr_str} cannot start or end with ' '
+
+passes-doc-alias-bad-location = {$attr_str} isn't allowed on {$location}
+
+passes-doc-alias-not-an-alias = {$attr_str} is the same as the item's name
+
+passes-doc-alias-duplicated = doc alias is duplicated
+    .label = first defined here
+
+passes-doc-alias-not-string-literal = `#[doc(alias("a"))]` expects string literals
+
+passes-doc-alias-malformed =
+    doc alias attribute expects a string `#[doc(alias = "a")]` or a list of strings `#[doc(alias("a", "b"))]`
+
+passes-doc-keyword-empty-mod = `#[doc(keyword = "...")]` should be used on empty modules
+
+passes-doc-keyword-not-mod = `#[doc(keyword = "...")]` should be used on modules
+
+passes-doc-keyword-invalid-ident = `{$doc_keyword}` is not a valid identifier
+
+passes-doc-tuple-variadic-not-first =
+    `#[doc(tuple_variadic)]` must be used on the first of a set of tuple trait impls with varying arity
+
+passes-doc-keyword-only-impl = `#[doc(keyword = "...")]` should be used on impl blocks
+
+passes-doc-inline-conflict-first = this attribute...
+passes-doc-inline-conflict-second = ...conflicts with this attribute
+passes-doc-inline-conflict = conflicting doc inlining attributes
+    .help = remove one of the conflicting attributes
+
+passes-doc-inline-only-use = this attribute can only be applied to a `use` item
+    .label = only applicable on `use` items
+    .not-a-use-item-label = not a `use` item
+    .note = read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#inline-and-no_inline> for more information
+
+passes-doc-attr-not-crate-level =
+    `#![doc({$attr_name} = "...")]` isn't allowed as a crate-level attribute
+
+passes-attr-crate-level = this attribute can only be applied at the crate level
+    .suggestion = to apply to the crate, use an inner attribute
+    .help = to apply to the crate, use an inner attribute
+    .note = read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level> for more information
+
+passes-doc-test-unknown = unknown `doc(test)` attribute `{$path}`
+
+passes-doc-test-takes-list = `#[doc(test(...)]` takes a list of attributes
+
+passes-doc-primitive = `doc(primitive)` should never have been stable
+
+passes-doc-test-unknown-any = unknown `doc` attribute `{$path}`
+
+passes-doc-test-unknown-spotlight = unknown `doc` attribute `{$path}`
+    .note = `doc(spotlight)` was renamed to `doc(notable_trait)`
+    .suggestion = use `notable_trait` instead
+    .no-op-note = `doc(spotlight)` is now a no-op
+
+passes-doc-test-unknown-include = unknown `doc` attribute `{$path}`
+    .suggestion = use `doc = include_str!` instead
+
+passes-doc-invalid = invalid `doc` attribute
+
+passes-pass-by-value = `pass_by_value` attribute should be applied to a struct, enum or type alias
+    .label = is not a struct, enum or type alias
+
+passes-allow-incoherent-impl =
+    `rustc_allow_incoherent_impl` attribute should be applied to impl items.
+    .label = the only currently supported targets are inherent methods
+
+passes-has-incoherent-inherent-impl =
+    `rustc_has_incoherent_inherent_impls` attribute should be applied to types or traits.
+    .label = only adts, extern types and traits are supported
+
+passes-must-use-async =
+    `must_use` attribute on `async` functions applies to the anonymous `Future` returned by the function, not the value within
+    .label = this attribute does nothing, the `Future`s returned by async functions are already `must_use`
+
+passes-must-use-no-effect = `#[must_use]` has no effect when applied to {$article} {$target}
+
+passes-must-not-suspend = `must_not_suspend` attribute should be applied to a struct, enum, or trait
+    .label = is not a struct, enum, or trait
+
+passes-cold = {passes-should-be-applied-to-fn}
+    .warn = {-passes-previously-accepted}
+    .label = {passes-should-be-applied-to-fn.label}
+
+passes-link = attribute should be applied to an `extern` block with non-Rust ABI
+    .warn = {-passes-previously-accepted}
+    .label = not an `extern` block
diff --git a/compiler/rustc_error_messages/locales/en-US/privacy.ftl b/compiler/rustc_error_messages/locales/en-US/privacy.ftl
index 2b0778f48caee..f8a750da93f8d 100644
--- a/compiler/rustc_error_messages/locales/en-US/privacy.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/privacy.ftl
@@ -10,3 +10,12 @@ privacy-unnamed-item-is-private = {$kind} is private
 privacy-in-public-interface = {$vis_descr} {$kind} `{$descr}` in public interface
     .label = can't leak {$vis_descr} {$kind}
     .visibility-label = `{$descr}` declared as {$vis_descr}
+
+privacy-from-private-dep-in-public-interface =
+    {$kind} `{$descr}` from private dependency '{$krate}' in public interface
+
+private-in-public-lint =
+    {$vis_descr} {$kind} `{$descr}` in public interface (error {$kind ->
+        [trait] E0445
+        *[other] E0446
+    })
diff --git a/compiler/rustc_error_messages/src/lib.rs b/compiler/rustc_error_messages/src/lib.rs
index d16171cb162d6..a3040f83fdfc7 100644
--- a/compiler/rustc_error_messages/src/lib.rs
+++ b/compiler/rustc_error_messages/src/lib.rs
@@ -37,6 +37,7 @@ fluent_messages! {
     expand => "../locales/en-US/expand.ftl",
     lint => "../locales/en-US/lint.ftl",
     parser => "../locales/en-US/parser.ftl",
+    passes => "../locales/en-US/passes.ftl",
     privacy => "../locales/en-US/privacy.ftl",
     typeck => "../locales/en-US/typeck.ftl",
 }
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index da321c4587509..7d7f3e1833576 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -40,6 +40,35 @@ pub trait IntoDiagnosticArg {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static>;
 }
 
+macro_rules! into_diagnostic_arg_using_display {
+    ($( $ty:ty ),+ $(,)?) => {
+        $(
+            impl IntoDiagnosticArg for $ty {
+                fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+                    self.to_string().into_diagnostic_arg()
+                }
+            }
+        )+
+    }
+}
+
+into_diagnostic_arg_using_display!(
+    i8,
+    u8,
+    i16,
+    u16,
+    i32,
+    u32,
+    i64,
+    u64,
+    i128,
+    u128,
+    std::num::NonZeroU32,
+    hir::Target,
+    Edition,
+    Ident,
+);
+
 impl IntoDiagnosticArg for bool {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
         if self {
@@ -50,81 +79,9 @@ impl IntoDiagnosticArg for bool {
     }
 }
 
-impl IntoDiagnosticArg for i8 {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl IntoDiagnosticArg for u8 {
+impl IntoDiagnosticArg for char {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl IntoDiagnosticArg for i16 {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl IntoDiagnosticArg for u16 {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl IntoDiagnosticArg for i32 {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl IntoDiagnosticArg for u32 {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl IntoDiagnosticArg for i64 {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl IntoDiagnosticArg for u64 {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl IntoDiagnosticArg for i128 {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl IntoDiagnosticArg for u128 {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl IntoDiagnosticArg for String {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self))
-    }
-}
-
-impl IntoDiagnosticArg for std::num::NonZeroU32 {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl IntoDiagnosticArg for Edition {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
+        DiagnosticArgValue::Str(Cow::Owned(format!("{:?}", self)))
     }
 }
 
@@ -134,15 +91,15 @@ impl IntoDiagnosticArg for Symbol {
     }
 }
 
-impl IntoDiagnosticArg for Ident {
+impl<'a> IntoDiagnosticArg for &'a str {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
         self.to_string().into_diagnostic_arg()
     }
 }
 
-impl<'a> IntoDiagnosticArg for &'a str {
+impl IntoDiagnosticArg for String {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        self.to_string().into_diagnostic_arg()
+        DiagnosticArgValue::Str(Cow::Owned(self))
     }
 }
 
@@ -496,7 +453,7 @@ impl Diagnostic {
         self
     }
 
-    pub fn note_trait_signature(&mut self, name: String, signature: String) -> &mut Self {
+    pub fn note_trait_signature(&mut self, name: Symbol, signature: String) -> &mut Self {
         self.highlighted_note(vec![
             (format!("`{}` from trait: `", name), Style::NoStyle),
             (signature, Style::Highlight),
diff --git a/compiler/rustc_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
index 99ac6a3546ed6..9e68ee282e652 100644
--- a/compiler/rustc_errors/src/diagnostic_builder.rs
+++ b/compiler/rustc_errors/src/diagnostic_builder.rs
@@ -595,6 +595,7 @@ macro_rules! error_code {
 pub struct LintDiagnosticBuilder<'a, G: EmissionGuarantee>(DiagnosticBuilder<'a, G>);
 
 impl<'a, G: EmissionGuarantee> LintDiagnosticBuilder<'a, G> {
+    #[rustc_lint_diagnostics]
     /// Return the inner `DiagnosticBuilder`, first setting the primary message to `msg`.
     pub fn build(mut self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'a, G> {
         self.0.set_primary_message(msg);
diff --git a/compiler/rustc_expand/src/module.rs b/compiler/rustc_expand/src/module.rs
index 876faad33b678..0315d11634c6b 100644
--- a/compiler/rustc_expand/src/module.rs
+++ b/compiler/rustc_expand/src/module.rs
@@ -218,10 +218,9 @@ pub fn default_submod_path<'a>(
         ""
     };
 
-    let mod_name = ident.name.to_string();
-    let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
+    let default_path_str = format!("{}{}.rs", relative_prefix, ident.name);
     let secondary_path_str =
-        format!("{}{}{}mod.rs", relative_prefix, mod_name, path::MAIN_SEPARATOR);
+        format!("{}{}{}mod.rs", relative_prefix, ident.name, path::MAIN_SEPARATOR);
     let default_path = dir_path.join(&default_path_str);
     let secondary_path = dir_path.join(&secondary_path_str);
     let default_exists = sess.source_map().file_exists(&default_path);
diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
index 066bf9681b6bb..b267140daa971 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
@@ -138,7 +138,7 @@ fn fmt_printer<'a, 'tcx>(infcx: &'a InferCtxt<'_, 'tcx>, ns: Namespace) -> FmtPr
         if let TypeVariableOriginKind::TypeParameterDefinition(name, _) =
             infcx.inner.borrow_mut().type_variables().var_origin(ty_vid).kind
         {
-            Some(name.to_string())
+            Some(name)
         } else {
             None
         }
@@ -151,7 +151,7 @@ fn fmt_printer<'a, 'tcx>(infcx: &'a InferCtxt<'_, 'tcx>, ns: Namespace) -> FmtPr
         if let ConstVariableOriginKind::ConstParameterDefinition(name, _) =
             infcx.inner.borrow_mut().const_unification_table().probe_value(ct_vid).origin.kind
         {
-            return Some(name.to_string());
+            return Some(name);
         } else {
             None
         }
diff --git a/compiler/rustc_macros/src/diagnostics/diagnostic.rs b/compiler/rustc_macros/src/diagnostics/diagnostic.rs
index 027f377b0acc7..6b5b8b5932018 100644
--- a/compiler/rustc_macros/src/diagnostics/diagnostic.rs
+++ b/compiler/rustc_macros/src/diagnostics/diagnostic.rs
@@ -59,7 +59,7 @@ impl<'a> SessionDiagnosticDerive<'a> {
                         return DiagnosticDeriveError::ErrorHandled.to_compile_error();
                     }
                     (Some(DiagnosticDeriveKind::Lint), _) => {
-                        span_err(span, "only `#[error(..)]` and `#[warn(..)]` are supported")
+                        span_err(span, "only `#[error(..)]` and `#[warning(..)]` are supported")
                             .help("use the `#[error(...)]` attribute to create a error")
                             .emit();
                         return DiagnosticDeriveError::ErrorHandled.to_compile_error();
diff --git a/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs b/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
index 74ce1ab08c264..5c5275b7cfb92 100644
--- a/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
+++ b/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
@@ -8,12 +8,13 @@ use crate::diagnostics::utils::{
     report_error_if_not_applied_to_span, report_type_error, type_is_unit, type_matches_path,
     Applicability, FieldInfo, FieldInnerTy, HasFieldMap, SetOnce,
 };
-use proc_macro2::{Ident, TokenStream};
+use proc_macro2::{Ident, Span, TokenStream};
 use quote::{format_ident, quote};
 use std::collections::HashMap;
 use std::str::FromStr;
 use syn::{
-    parse_quote, spanned::Spanned, Attribute, Meta, MetaList, MetaNameValue, NestedMeta, Path, Type,
+    parse_quote, spanned::Spanned, Attribute, Field, Meta, MetaList, MetaNameValue, NestedMeta,
+    Path, Type,
 };
 use synstructure::{BindingInfo, Structure};
 
@@ -80,8 +81,8 @@ impl DiagnosticDeriveBuilder {
     }
 
     pub fn body<'s>(&mut self, structure: &mut Structure<'s>) -> (TokenStream, TokenStream) {
-        // Keep track of which fields are subdiagnostics or have no attributes.
-        let mut subdiagnostics_or_empty = std::collections::HashSet::new();
+        // Keep track of which fields need to be handled with a by-move binding.
+        let mut needs_moved = std::collections::HashSet::new();
 
         // Generates calls to `span_label` and similar functions based on the attributes
         // on fields. Code for suggestions uses formatting machinery and the value of
@@ -92,16 +93,11 @@ impl DiagnosticDeriveBuilder {
         let attrs = structure
             .clone()
             .filter(|field_binding| {
-                let attrs = &field_binding.ast().attrs;
-
-                (!attrs.is_empty()
-                    && attrs.iter().all(|attr| {
-                        "subdiagnostic" != attr.path.segments.last().unwrap().ident.to_string()
-                    }))
-                    || {
-                        subdiagnostics_or_empty.insert(field_binding.binding.clone());
-                        false
-                    }
+                let ast = &field_binding.ast();
+                !self.needs_move(ast) || {
+                    needs_moved.insert(field_binding.binding.clone());
+                    false
+                }
             })
             .each(|field_binding| self.generate_field_attrs_code(field_binding));
 
@@ -111,12 +107,41 @@ impl DiagnosticDeriveBuilder {
         // attributes or a `#[subdiagnostic]` attribute then it must be passed as an
         // argument to the diagnostic so that it can be referred to by Fluent messages.
         let args = structure
-            .filter(|field_binding| subdiagnostics_or_empty.contains(&field_binding.binding))
+            .filter(|field_binding| needs_moved.contains(&field_binding.binding))
             .each(|field_binding| self.generate_field_attrs_code(field_binding));
 
         (attrs, args)
     }
 
+    /// Returns `true` if `field` should generate a `set_arg` call rather than any other diagnostic
+    /// call (like `span_label`).
+    fn should_generate_set_arg(&self, field: &Field) -> bool {
+        field.attrs.is_empty()
+    }
+
+    /// Returns `true` if `field` needs to have code generated in the by-move branch of the
+    /// generated derive rather than the by-ref branch.
+    fn needs_move(&self, field: &Field) -> bool {
+        let generates_set_arg = self.should_generate_set_arg(field);
+        let is_multispan = type_matches_path(&field.ty, &["rustc_errors", "MultiSpan"]);
+        // FIXME(davidtwco): better support for one field needing to be in the by-move and
+        // by-ref branches.
+        let is_subdiagnostic = field
+            .attrs
+            .iter()
+            .map(|attr| attr.path.segments.last().unwrap().ident.to_string())
+            .any(|attr| attr == "subdiagnostic");
+
+        // `set_arg` calls take their argument by-move..
+        generates_set_arg
+            // If this is a `MultiSpan` field then it needs to be moved to be used by any
+            // attribute..
+            || is_multispan
+            // If this a `#[subdiagnostic]` then it needs to be moved as the other diagnostic is
+            // unlikely to be `Copy`..
+            || is_subdiagnostic
+    }
+
     /// Establishes state in the `DiagnosticDeriveBuilder` resulting from the struct
     /// attributes like `#[error(..)`, such as the diagnostic kind and slug. Generates
     /// diagnostic builder calls for setting error code and creating note/help messages.
@@ -131,7 +156,7 @@ impl DiagnosticDeriveBuilder {
         let name = name.as_str();
         let meta = attr.parse_meta()?;
 
-        let is_help_or_note = matches!(name, "help" | "note");
+        let is_help_note_or_warn = matches!(name, "help" | "note" | "warn_");
 
         let nested = match meta {
             // Most attributes are lists, like `#[error(..)]`/`#[warning(..)]` for most cases or
@@ -139,8 +164,12 @@ impl DiagnosticDeriveBuilder {
             Meta::List(MetaList { ref nested, .. }) => nested,
             // Subdiagnostics without spans can be applied to the type too, and these are just
             // paths: `#[help]` and `#[note]`
-            Meta::Path(_) if is_help_or_note => {
-                let fn_name = proc_macro2::Ident::new(name, attr.span());
+            Meta::Path(_) if is_help_note_or_warn => {
+                let fn_name = if name == "warn_" {
+                    Ident::new("warn", attr.span())
+                } else {
+                    Ident::new(name, attr.span())
+                };
                 return Ok(quote! { #diag.#fn_name(rustc_errors::fluent::_subdiag::#fn_name); });
             }
             _ => throw_invalid_attr!(attr, &meta),
@@ -152,9 +181,11 @@ impl DiagnosticDeriveBuilder {
             "error" => self.kind.set_once((DiagnosticDeriveKind::Error, span)),
             "warning" => self.kind.set_once((DiagnosticDeriveKind::Warn, span)),
             "lint" => self.kind.set_once((DiagnosticDeriveKind::Lint, span)),
-            "help" | "note" => (),
+            "help" | "note" | "warn_" => (),
             _ => throw_invalid_attr!(attr, &meta, |diag| {
-                diag.help("only `error`, `warning`, `help` and `note` are valid attributes")
+                diag.help(
+                    "only `error`, `warning`, `help`, `note` and `warn_` are valid attributes",
+                )
             }),
         }
 
@@ -163,14 +194,16 @@ impl DiagnosticDeriveBuilder {
         let mut nested_iter = nested.into_iter();
         if let Some(nested_attr) = nested_iter.next() {
             // Report an error if there are any other list items after the path.
-            if is_help_or_note && nested_iter.next().is_some() {
+            if is_help_note_or_warn && nested_iter.next().is_some() {
                 throw_invalid_nested_attr!(attr, &nested_attr, |diag| {
-                    diag.help("`help` and `note` struct attributes can only have one argument")
+                    diag.help(
+                        "`help`, `note` and `warn_` struct attributes can only have one argument",
+                    )
                 });
             }
 
             match nested_attr {
-                NestedMeta::Meta(Meta::Path(path)) if is_help_or_note => {
+                NestedMeta::Meta(Meta::Path(path)) if is_help_note_or_warn => {
                     let fn_name = proc_macro2::Ident::new(name, attr.span());
                     return Ok(quote! { #diag.#fn_name(rustc_errors::fluent::#path); });
                 }
@@ -178,7 +211,7 @@ impl DiagnosticDeriveBuilder {
                     self.slug.set_once((path.clone(), span));
                 }
                 NestedMeta::Meta(meta @ Meta::NameValue(_))
-                    if !is_help_or_note
+                    if !is_help_note_or_warn
                         && meta.path().segments.last().unwrap().ident.to_string() == "code" =>
                 {
                     // don't error for valid follow-up attributes
@@ -227,57 +260,55 @@ impl DiagnosticDeriveBuilder {
         let field = binding_info.ast();
         let field_binding = &binding_info.binding;
 
-        let inner_ty = FieldInnerTy::from_type(&field.ty);
-
-        // When generating `set_arg` or `add_subdiagnostic` calls, move data rather than
-        // borrow it to avoid requiring clones - this must therefore be the last use of
-        // each field (for example, any formatting machinery that might refer to a field
-        // should be generated already).
-        if field.attrs.is_empty() {
+        if self.should_generate_set_arg(&field) {
             let diag = &self.diag;
             let ident = field.ident.as_ref().unwrap();
-            quote! {
+            return quote! {
                 #diag.set_arg(
                     stringify!(#ident),
                     #field_binding
                 );
-            }
-        } else {
-            field
-                .attrs
-                .iter()
-                .map(move |attr| {
-                    let name = attr.path.segments.last().unwrap().ident.to_string();
-                    let (binding, needs_destructure) = match (name.as_str(), &inner_ty) {
-                        // `primary_span` can accept a `Vec<Span>` so don't destructure that.
-                        ("primary_span", FieldInnerTy::Vec(_)) => {
-                            (quote! { #field_binding.clone() }, false)
-                        }
-                        // `subdiagnostics` are not derefed because they are bound by value.
-                        ("subdiagnostic", _) => (quote! { #field_binding }, true),
-                        _ => (quote! { *#field_binding }, true),
-                    };
-
-                    let generated_code = self
-                        .generate_inner_field_code(
-                            attr,
-                            FieldInfo {
-                                binding: binding_info,
-                                ty: inner_ty.inner_type().unwrap_or(&field.ty),
-                                span: &field.span(),
-                            },
-                            binding,
-                        )
-                        .unwrap_or_else(|v| v.to_compile_error());
-
-                    if needs_destructure {
-                        inner_ty.with(field_binding, generated_code)
-                    } else {
-                        generated_code
-                    }
-                })
-                .collect()
+            };
         }
+
+        let needs_move = self.needs_move(&field);
+        let inner_ty = FieldInnerTy::from_type(&field.ty);
+
+        field
+            .attrs
+            .iter()
+            .map(move |attr| {
+                let name = attr.path.segments.last().unwrap().ident.to_string();
+                let needs_clone =
+                    name == "primary_span" && matches!(inner_ty, FieldInnerTy::Vec(_));
+                let (binding, needs_destructure) = if needs_clone {
+                    // `primary_span` can accept a `Vec<Span>` so don't destructure that.
+                    (quote! { #field_binding.clone() }, false)
+                } else if needs_move {
+                    (quote! { #field_binding }, true)
+                } else {
+                    (quote! { *#field_binding }, true)
+                };
+
+                let generated_code = self
+                    .generate_inner_field_code(
+                        attr,
+                        FieldInfo {
+                            binding: binding_info,
+                            ty: inner_ty.inner_type().unwrap_or(&field.ty),
+                            span: &field.span(),
+                        },
+                        binding,
+                    )
+                    .unwrap_or_else(|v| v.to_compile_error());
+
+                if needs_destructure {
+                    inner_ty.with(field_binding, generated_code)
+                } else {
+                    generated_code
+                }
+            })
+            .collect()
     }
 
     fn generate_inner_field_code(
@@ -324,10 +355,12 @@ impl DiagnosticDeriveBuilder {
                 report_error_if_not_applied_to_span(attr, &info)?;
                 Ok(self.add_spanned_subdiagnostic(binding, ident, parse_quote! { _subdiag::label }))
             }
-            "note" | "help" => {
-                let path = match name {
-                    "note" => parse_quote! { _subdiag::note },
-                    "help" => parse_quote! { _subdiag::help },
+            "note" | "help" | "warn_" => {
+                let warn_ident = Ident::new("warn", Span::call_site());
+                let (ident, path) = match name {
+                    "note" => (ident, parse_quote! { _subdiag::note }),
+                    "help" => (ident, parse_quote! { _subdiag::help }),
+                    "warn_" => (&warn_ident, parse_quote! { _subdiag::warn }),
                     _ => unreachable!(),
                 };
                 if type_matches_path(&info.ty, &["rustc_span", "Span"]) {
@@ -364,10 +397,10 @@ impl DiagnosticDeriveBuilder {
             "suggestion" | "suggestion_short" | "suggestion_hidden" | "suggestion_verbose" => {
                 return self.generate_inner_field_code_suggestion(attr, info);
             }
-            "label" | "help" | "note" => (),
+            "label" | "help" | "note" | "warn_" => (),
             _ => throw_invalid_attr!(attr, &meta, |diag| {
                 diag.help(
-                    "only `label`, `note`, `help` or `suggestion{,_short,_hidden,_verbose}` are \
+                    "only `label`, `help`, `note`, `warn` or `suggestion{,_short,_hidden,_verbose}` are \
                      valid field attributes",
                 )
             }),
@@ -396,7 +429,14 @@ impl DiagnosticDeriveBuilder {
                 Ok(self.add_spanned_subdiagnostic(binding, ident, msg))
             }
             "note" | "help" if type_is_unit(&info.ty) => Ok(self.add_subdiagnostic(ident, msg)),
-            "note" | "help" => report_type_error(attr, "`Span` or `()`")?,
+            // `warn_` must be special-cased because the attribute `warn` already has meaning and
+            // so isn't used, despite the diagnostic API being named `warn`.
+            "warn_" if type_matches_path(&info.ty, &["rustc_span", "Span"]) => Ok(self
+                .add_spanned_subdiagnostic(binding, &Ident::new("warn", Span::call_site()), msg)),
+            "warn_" if type_is_unit(&info.ty) => {
+                Ok(self.add_subdiagnostic(&Ident::new("warn", Span::call_site()), msg))
+            }
+            "note" | "help" | "warn_" => report_type_error(attr, "`Span` or `()`")?,
             _ => unreachable!(),
         }
     }
diff --git a/compiler/rustc_macros/src/diagnostics/fluent.rs b/compiler/rustc_macros/src/diagnostics/fluent.rs
index 2758fcd1310fe..1170d2b3c59a4 100644
--- a/compiler/rustc_macros/src/diagnostics/fluent.rs
+++ b/compiler/rustc_macros/src/diagnostics/fluent.rs
@@ -260,10 +260,12 @@ pub(crate) fn fluent_messages(input: proc_macro::TokenStream) -> proc_macro::Tok
             #generated
 
             pub mod _subdiag {
-                pub const note: crate::SubdiagnosticMessage =
-                    crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("note"));
                 pub const help: crate::SubdiagnosticMessage =
                     crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("help"));
+                pub const note: crate::SubdiagnosticMessage =
+                    crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("note"));
+                pub const warn: crate::SubdiagnosticMessage =
+                    crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("warn"));
                 pub const label: crate::SubdiagnosticMessage =
                     crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("label"));
                 pub const suggestion: crate::SubdiagnosticMessage =
diff --git a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
index 2a5b6beba94bb..edf4dbed9853e 100644
--- a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
+++ b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
@@ -37,6 +37,8 @@ enum SubdiagnosticKind {
     Note,
     /// `#[help(...)]`
     Help,
+    /// `#[warn_(...)]`
+    Warn,
     /// `#[suggestion{,_short,_hidden,_verbose}]`
     Suggestion(SubdiagnosticSuggestionKind),
 }
@@ -49,6 +51,7 @@ impl FromStr for SubdiagnosticKind {
             "label" => Ok(SubdiagnosticKind::Label),
             "note" => Ok(SubdiagnosticKind::Note),
             "help" => Ok(SubdiagnosticKind::Help),
+            "warn_" => Ok(SubdiagnosticKind::Warn),
             "suggestion" => Ok(SubdiagnosticKind::Suggestion(SubdiagnosticSuggestionKind::Normal)),
             "suggestion_short" => {
                 Ok(SubdiagnosticKind::Suggestion(SubdiagnosticSuggestionKind::Short))
@@ -70,6 +73,7 @@ impl quote::IdentFragment for SubdiagnosticKind {
             SubdiagnosticKind::Label => write!(f, "label"),
             SubdiagnosticKind::Note => write!(f, "note"),
             SubdiagnosticKind::Help => write!(f, "help"),
+            SubdiagnosticKind::Warn => write!(f, "warn"),
             SubdiagnosticKind::Suggestion(SubdiagnosticSuggestionKind::Normal) => {
                 write!(f, "suggestion")
             }
diff --git a/compiler/rustc_macros/src/diagnostics/utils.rs b/compiler/rustc_macros/src/diagnostics/utils.rs
index 8977db4606c56..002abb152f759 100644
--- a/compiler/rustc_macros/src/diagnostics/utils.rs
+++ b/compiler/rustc_macros/src/diagnostics/utils.rs
@@ -85,7 +85,13 @@ pub(crate) fn report_error_if_not_applied_to_span(
     attr: &Attribute,
     info: &FieldInfo<'_>,
 ) -> Result<(), DiagnosticDeriveError> {
-    report_error_if_not_applied_to_ty(attr, info, &["rustc_span", "Span"], "`Span`")
+    if !type_matches_path(&info.ty, &["rustc_span", "Span"])
+        && !type_matches_path(&info.ty, &["rustc_errors", "MultiSpan"])
+    {
+        report_type_error(attr, "`Span` or `MultiSpan`")?;
+    }
+
+    Ok(())
 }
 
 /// Inner type of a field and type of wrapper.
diff --git a/compiler/rustc_macros/src/lib.rs b/compiler/rustc_macros/src/lib.rs
index 168530c54b99e..ab509b26f1c55 100644
--- a/compiler/rustc_macros/src/lib.rs
+++ b/compiler/rustc_macros/src/lib.rs
@@ -130,8 +130,9 @@ decl_derive!(
         warning,
         error,
         lint,
-        note,
         help,
+        note,
+        warn_,
         // field attributes
         skip_arg,
         primary_span,
@@ -148,8 +149,9 @@ decl_derive!(
         warning,
         error,
         lint,
-        note,
         help,
+        note,
+        warn_,
         // field attributes
         skip_arg,
         primary_span,
@@ -166,6 +168,7 @@ decl_derive!(
         label,
         help,
         note,
+        warn_,
         suggestion,
         suggestion_short,
         suggestion_hidden,
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index f61cb7e8c472e..0b5d23be58d85 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -1397,6 +1397,7 @@ impl<V, T> ProjectionElem<V, T> {
 
             Self::Field(_, _)
             | Self::Index(_)
+            | Self::OpaqueCast(_)
             | Self::ConstantIndex { .. }
             | Self::Subslice { .. }
             | Self::Downcast(_, _) => false,
@@ -1574,7 +1575,9 @@ impl Debug for Place<'_> {
     fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
         for elem in self.projection.iter().rev() {
             match elem {
-                ProjectionElem::Downcast(_, _) | ProjectionElem::Field(_, _) => {
+                ProjectionElem::OpaqueCast(_)
+                | ProjectionElem::Downcast(_, _)
+                | ProjectionElem::Field(_, _) => {
                     write!(fmt, "(").unwrap();
                 }
                 ProjectionElem::Deref => {
@@ -1590,6 +1593,9 @@ impl Debug for Place<'_> {
 
         for elem in self.projection.iter() {
             match elem {
+                ProjectionElem::OpaqueCast(ty) => {
+                    write!(fmt, " as {})", ty)?;
+                }
                 ProjectionElem::Downcast(Some(name), _index) => {
                     write!(fmt, " as {})", name)?;
                 }
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index 510316c778bc7..263c2ca3c700e 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -754,6 +754,9 @@ pub type AssertMessage<'tcx> = AssertKind<Operand<'tcx>>;
 ///    generator has more than one variant, the parent place's variant index must be set, indicating
 ///    which variant is being used. If it has just one variant, the variant index may or may not be
 ///    included - the single possible variant is inferred if it is not included.
+///  - [`OpaqueCast`](ProjectionElem::OpaqueCast): This projection changes the place's type to the
+///    given one, and makes no other changes. A `OpaqueCast` projection on any type other than an
+///    opaque type from the current crate is not well-formed.
 ///  - [`ConstantIndex`](ProjectionElem::ConstantIndex): Computes an offset in units of `T` into the
 ///    place as described in the documentation for the `ProjectionElem`. The resulting address is
 ///    the parent's address plus that offset, and the type is `T`. This is only legal if the parent
@@ -856,6 +859,10 @@ pub enum ProjectionElem<V, T> {
     ///
     /// The included Symbol is the name of the variant, used for printing MIR.
     Downcast(Option<Symbol>, VariantIdx),
+
+    /// Like an explicit cast from an opaque type to a concrete type, but without
+    /// requiring an intermediate variable.
+    OpaqueCast(T),
 }
 
 /// Alias for projections as they appear in places, where the base is a place
diff --git a/compiler/rustc_middle/src/mir/tcx.rs b/compiler/rustc_middle/src/mir/tcx.rs
index fd3359ea80fe5..c6975df45efc2 100644
--- a/compiler/rustc_middle/src/mir/tcx.rs
+++ b/compiler/rustc_middle/src/mir/tcx.rs
@@ -57,7 +57,7 @@ impl<'tcx> PlaceTy<'tcx> {
     /// `PlaceElem`, where we can just use the `Ty` that is already
     /// stored inline on field projection elems.
     pub fn projection_ty(self, tcx: TyCtxt<'tcx>, elem: PlaceElem<'tcx>) -> PlaceTy<'tcx> {
-        self.projection_ty_core(tcx, ty::ParamEnv::empty(), &elem, |_, _, ty| ty)
+        self.projection_ty_core(tcx, ty::ParamEnv::empty(), &elem, |_, _, ty| ty, |_, ty| ty)
     }
 
     /// `place_ty.projection_ty_core(tcx, elem, |...| { ... })`
@@ -71,6 +71,7 @@ impl<'tcx> PlaceTy<'tcx> {
         param_env: ty::ParamEnv<'tcx>,
         elem: &ProjectionElem<V, T>,
         mut handle_field: impl FnMut(&Self, Field, T) -> Ty<'tcx>,
+        mut handle_opaque_cast: impl FnMut(&Self, T) -> Ty<'tcx>,
     ) -> PlaceTy<'tcx>
     where
         V: ::std::fmt::Debug,
@@ -109,6 +110,7 @@ impl<'tcx> PlaceTy<'tcx> {
                 PlaceTy { ty: self.ty, variant_index: Some(index) }
             }
             ProjectionElem::Field(f, fty) => PlaceTy::from_ty(handle_field(&self, f, fty)),
+            ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(handle_opaque_cast(&self, ty)),
         };
         debug!("projection_ty self: {:?} elem: {:?} yields: {:?}", self, elem, answer);
         answer
diff --git a/compiler/rustc_middle/src/mir/type_foldable.rs b/compiler/rustc_middle/src/mir/type_foldable.rs
index 82a6b0c506f58..a73ef23e28132 100644
--- a/compiler/rustc_middle/src/mir/type_foldable.rs
+++ b/compiler/rustc_middle/src/mir/type_foldable.rs
@@ -182,6 +182,7 @@ impl<'tcx> TypeFoldable<'tcx> for PlaceElem<'tcx> {
         Ok(match self {
             Deref => Deref,
             Field(f, ty) => Field(f, ty.try_fold_with(folder)?),
+            OpaqueCast(ty) => OpaqueCast(ty.try_fold_with(folder)?),
             Index(v) => Index(v.try_fold_with(folder)?),
             Downcast(symbol, variantidx) => Downcast(symbol, variantidx),
             ConstantIndex { offset, min_length, from_end } => {
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index d285728ec0783..e5599fb15ad31 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -1064,6 +1064,11 @@ macro_rules! visit_place_fns {
                     self.visit_ty(&mut new_ty, TyContext::Location(location));
                     if ty != new_ty { Some(PlaceElem::Field(field, new_ty)) } else { None }
                 }
+                PlaceElem::OpaqueCast(ty) => {
+                    let mut new_ty = ty;
+                    self.visit_ty(&mut new_ty, TyContext::Location(location));
+                    if ty != new_ty { Some(PlaceElem::OpaqueCast(new_ty)) } else { None }
+                }
                 PlaceElem::Deref
                 | PlaceElem::ConstantIndex { .. }
                 | PlaceElem::Subslice { .. }
@@ -1133,7 +1138,7 @@ macro_rules! visit_place_fns {
             location: Location,
         ) {
             match elem {
-                ProjectionElem::Field(_field, ty) => {
+                ProjectionElem::OpaqueCast(ty) | ProjectionElem::Field(_, ty) => {
                     self.visit_ty(ty, TyContext::Location(location));
                 }
                 ProjectionElem::Index(local) => {
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index 945cdfbb0e978..75559d4f8b843 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -542,17 +542,9 @@ pub enum SelectionError<'tcx> {
     ErrorReporting,
     /// Multiple applicable `impl`s where found. The `DefId`s correspond to
     /// all the `impl`s' Items.
-    Ambiguous(Vec<AmbiguousSelection>),
+    Ambiguous(Vec<DefId>),
 }
 
-#[derive(Copy, Clone, Debug)]
-pub enum AmbiguousSelection {
-    Impl(DefId),
-    ParamEnv(Span),
-}
-
-TrivialTypeTraversalAndLiftImpls! { AmbiguousSelection, }
-
 /// When performing resolution, it is typically the case that there
 /// can be one of three outcomes:
 ///
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 71c93d05792c5..c41a8318ec57f 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -1975,7 +1975,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                         min_size = field_end;
                     }
                     FieldInfo {
-                        name: name.to_string(),
+                        name,
                         offset: offset.bytes(),
                         size: field_layout.size.bytes(),
                         align: field_layout.align.abi.bytes(),
@@ -1984,7 +1984,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                 .collect();
 
             VariantInfo {
-                name: n.map(|n| n.to_string()),
+                name: n,
                 kind: if layout.is_unsized() { SizeKind::Min } else { SizeKind::Exact },
                 align: layout.align.abi.bytes(),
                 size: if min_size.bytes() == 0 { layout.size.bytes() } else { min_size.bytes() },
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 81c4d2ae34671..96e84bc8f0acf 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1030,11 +1030,11 @@ pub trait PrettyPrinter<'tcx>:
         }
     }
 
-    fn ty_infer_name(&self, _: ty::TyVid) -> Option<String> {
+    fn ty_infer_name(&self, _: ty::TyVid) -> Option<Symbol> {
         None
     }
 
-    fn const_infer_name(&self, _: ty::ConstVid<'tcx>) -> Option<String> {
+    fn const_infer_name(&self, _: ty::ConstVid<'tcx>) -> Option<Symbol> {
         None
     }
 
@@ -1550,8 +1550,8 @@ pub struct FmtPrinterData<'a, 'tcx> {
 
     pub region_highlight_mode: RegionHighlightMode<'tcx>,
 
-    pub ty_infer_name_resolver: Option<Box<dyn Fn(ty::TyVid) -> Option<String> + 'a>>,
-    pub const_infer_name_resolver: Option<Box<dyn Fn(ty::ConstVid<'tcx>) -> Option<String> + 'a>>,
+    pub ty_infer_name_resolver: Option<Box<dyn Fn(ty::TyVid) -> Option<Symbol> + 'a>>,
+    pub const_infer_name_resolver: Option<Box<dyn Fn(ty::ConstVid<'tcx>) -> Option<Symbol> + 'a>>,
 }
 
 impl<'a, 'tcx> Deref for FmtPrinter<'a, 'tcx> {
@@ -1841,11 +1841,11 @@ impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
 }
 
 impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
-    fn ty_infer_name(&self, id: ty::TyVid) -> Option<String> {
+    fn ty_infer_name(&self, id: ty::TyVid) -> Option<Symbol> {
         self.0.ty_infer_name_resolver.as_ref().and_then(|func| func(id))
     }
 
-    fn const_infer_name(&self, id: ty::ConstVid<'tcx>) -> Option<String> {
+    fn const_infer_name(&self, id: ty::ConstVid<'tcx>) -> Option<Symbol> {
         self.0.const_infer_name_resolver.as_ref().and_then(|func| func(id))
     }
 
diff --git a/compiler/rustc_mir_build/src/build/expr/as_place.rs b/compiler/rustc_mir_build/src/build/expr/as_place.rs
index e88f9dc1f08f5..6abf419dd4991 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_place.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_place.rs
@@ -7,6 +7,7 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::hir::place::Projection as HirProjection;
 use rustc_middle::hir::place::ProjectionKind as HirProjectionKind;
 use rustc_middle::middle::region;
+use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::AssertKind::BoundsCheck;
 use rustc_middle::mir::*;
 use rustc_middle::thir::*;
@@ -71,7 +72,7 @@ pub(crate) enum PlaceBase {
 /// This is used internally when building a place for an expression like `a.b.c`. The fields `b`
 /// and `c` can be progressively pushed onto the place builder that is created when converting `a`.
 #[derive(Clone, Debug, PartialEq)]
-pub(crate) struct PlaceBuilder<'tcx> {
+pub(in crate::build) struct PlaceBuilder<'tcx> {
     base: PlaceBase,
     projection: Vec<PlaceElem<'tcx>>,
 }
@@ -104,6 +105,8 @@ fn convert_to_hir_projections_and_truncate_for_capture<'tcx>(
                 variant = Some(*idx);
                 continue;
             }
+            // These do not affect anything, they just make sure we know the right type.
+            ProjectionElem::OpaqueCast(_) => continue,
             ProjectionElem::Index(..)
             | ProjectionElem::ConstantIndex { .. }
             | ProjectionElem::Subslice { .. } => {
@@ -201,10 +204,10 @@ fn find_capture_matching_projections<'a, 'tcx>(
 /// `PlaceBuilder` now starts from `PlaceBase::Local`.
 ///
 /// Returns a Result with the error being the PlaceBuilder (`from_builder`) that was not found.
-fn to_upvars_resolved_place_builder<'a, 'tcx>(
+#[instrument(level = "trace", skip(cx))]
+fn to_upvars_resolved_place_builder<'tcx>(
     from_builder: PlaceBuilder<'tcx>,
-    tcx: TyCtxt<'tcx>,
-    typeck_results: &'a ty::TypeckResults<'tcx>,
+    cx: &Builder<'_, 'tcx>,
 ) -> Result<PlaceBuilder<'tcx>, PlaceBuilder<'tcx>> {
     match from_builder.base {
         PlaceBase::Local(_) => Ok(from_builder),
@@ -219,13 +222,13 @@ fn to_upvars_resolved_place_builder<'a, 'tcx>(
 
             let Some((capture_index, capture)) =
                 find_capture_matching_projections(
-                    typeck_results,
+                    cx.typeck_results,
                     var_hir_id,
                     closure_def_id,
                     &from_builder.projection,
                 ) else {
-                let closure_span = tcx.def_span(closure_def_id);
-                if !enable_precise_capture(tcx, closure_span) {
+                let closure_span = cx.tcx.def_span(closure_def_id);
+                if !enable_precise_capture(cx.tcx, closure_span) {
                     bug!(
                         "No associated capture found for {:?}[{:#?}] even though \
                             capture_disjoint_fields isn't enabled",
@@ -242,8 +245,8 @@ fn to_upvars_resolved_place_builder<'a, 'tcx>(
             };
 
             // We won't be building MIR if the closure wasn't local
-            let closure_hir_id = tcx.hir().local_def_id_to_hir_id(closure_def_id.expect_local());
-            let closure_ty = typeck_results.node_type(closure_hir_id);
+            let closure_hir_id = cx.tcx.hir().local_def_id_to_hir_id(closure_def_id.expect_local());
+            let closure_ty = cx.typeck_results.node_type(closure_hir_id);
 
             let substs = match closure_ty.kind() {
                 ty::Closure(_, substs) => ty::UpvarSubsts::Closure(substs),
@@ -270,12 +273,14 @@ fn to_upvars_resolved_place_builder<'a, 'tcx>(
 
             // We used some of the projections to build the capture itself,
             // now we apply the remaining to the upvar resolved place.
+            trace!(?capture.place, ?from_builder.projection);
             let remaining_projections = strip_prefix(
                 capture.place.base_ty,
                 from_builder.projection,
                 &capture.place.projections,
             );
             upvar_resolved_place_builder.projection.extend(remaining_projections);
+            trace!(?upvar_resolved_place_builder);
 
             Ok(upvar_resolved_place_builder)
         }
@@ -294,16 +299,21 @@ fn strip_prefix<'tcx>(
     prefix_projections: &[HirProjection<'tcx>],
 ) -> impl Iterator<Item = PlaceElem<'tcx>> {
     let mut iter = projections.into_iter();
+    let mut next = || match iter.next()? {
+        // Filter out opaque casts, they are unnecessary in the prefix.
+        ProjectionElem::OpaqueCast(..) => iter.next(),
+        other => Some(other),
+    };
     for projection in prefix_projections {
         match projection.kind {
             HirProjectionKind::Deref => {
-                assert!(matches!(iter.next(), Some(ProjectionElem::Deref)));
+                assert!(matches!(next(), Some(ProjectionElem::Deref)));
             }
             HirProjectionKind::Field(..) => {
                 if base_ty.is_enum() {
-                    assert!(matches!(iter.next(), Some(ProjectionElem::Downcast(..))));
+                    assert!(matches!(next(), Some(ProjectionElem::Downcast(..))));
                 }
-                assert!(matches!(iter.next(), Some(ProjectionElem::Field(..))));
+                assert!(matches!(next(), Some(ProjectionElem::Field(..))));
             }
             HirProjectionKind::Index | HirProjectionKind::Subslice => {
                 bug!("unexpected projection kind: {:?}", projection);
@@ -315,24 +325,32 @@ fn strip_prefix<'tcx>(
 }
 
 impl<'tcx> PlaceBuilder<'tcx> {
-    pub(crate) fn into_place<'a>(
-        self,
-        tcx: TyCtxt<'tcx>,
-        typeck_results: &'a ty::TypeckResults<'tcx>,
-    ) -> Place<'tcx> {
+    pub(crate) fn into_place(self, cx: &Builder<'_, 'tcx>) -> Place<'tcx> {
         if let PlaceBase::Local(local) = self.base {
-            Place { local, projection: tcx.intern_place_elems(&self.projection) }
+            let mut projections = vec![];
+            let mut ty = PlaceTy::from_ty(cx.local_decls[local].ty);
+            for projection in self.projection {
+                // Only preserve those opaque casts that actually go from an opaque type
+                // to another type.
+                if let ProjectionElem::OpaqueCast(t) = projection {
+                    if let ty::Opaque(..) = ty.ty.kind() {
+                        if t != ty.ty {
+                            projections.push(ProjectionElem::OpaqueCast(t));
+                        }
+                    }
+                } else {
+                    projections.push(projection);
+                }
+                ty = ty.projection_ty(cx.tcx, projection);
+            }
+            Place { local, projection: cx.tcx.intern_place_elems(&projections) }
         } else {
-            self.expect_upvars_resolved(tcx, typeck_results).into_place(tcx, typeck_results)
+            self.expect_upvars_resolved(cx).into_place(cx)
         }
     }
 
-    fn expect_upvars_resolved<'a>(
-        self,
-        tcx: TyCtxt<'tcx>,
-        typeck_results: &'a ty::TypeckResults<'tcx>,
-    ) -> PlaceBuilder<'tcx> {
-        to_upvars_resolved_place_builder(self, tcx, typeck_results).unwrap()
+    fn expect_upvars_resolved(self, cx: &Builder<'_, 'tcx>) -> PlaceBuilder<'tcx> {
+        to_upvars_resolved_place_builder(self, cx).unwrap()
     }
 
     /// Attempts to resolve the `PlaceBuilder`.
@@ -346,12 +364,11 @@ impl<'tcx> PlaceBuilder<'tcx> {
     /// not captured. This can happen because the final mir that will be
     /// generated doesn't require a read for this place. Failures will only
     /// happen inside closures.
-    pub(crate) fn try_upvars_resolved<'a>(
+    pub(crate) fn try_upvars_resolved(
         self,
-        tcx: TyCtxt<'tcx>,
-        typeck_results: &'a ty::TypeckResults<'tcx>,
+        cx: &Builder<'_, 'tcx>,
     ) -> Result<PlaceBuilder<'tcx>, PlaceBuilder<'tcx>> {
-        to_upvars_resolved_place_builder(self, tcx, typeck_results)
+        to_upvars_resolved_place_builder(self, cx)
     }
 
     pub(crate) fn base(&self) -> PlaceBase {
@@ -411,7 +428,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         expr: &Expr<'tcx>,
     ) -> BlockAnd<Place<'tcx>> {
         let place_builder = unpack!(block = self.as_place_builder(block, expr));
-        block.and(place_builder.into_place(self.tcx, self.typeck_results))
+        block.and(place_builder.into_place(self))
     }
 
     /// This is used when constructing a compound `Place`, so that we can avoid creating
@@ -435,7 +452,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         expr: &Expr<'tcx>,
     ) -> BlockAnd<Place<'tcx>> {
         let place_builder = unpack!(block = self.as_read_only_place_builder(block, expr));
-        block.and(place_builder.into_place(self.tcx, self.typeck_results))
+        block.and(place_builder.into_place(self))
     }
 
     /// This is used when constructing a compound `Place`, so that we can avoid creating
@@ -530,7 +547,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             inferred_ty: expr.ty,
                         });
 
-                    let place = place_builder.clone().into_place(this.tcx, this.typeck_results);
+                    let place = place_builder.clone().into_place(this);
                     this.cfg.push(
                         block,
                         Statement {
@@ -682,7 +699,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         if is_outermost_index {
             self.read_fake_borrows(block, fake_borrow_temps, source_info)
         } else {
-            base_place = base_place.expect_upvars_resolved(self.tcx, self.typeck_results);
+            base_place = base_place.expect_upvars_resolved(self);
             self.add_fake_borrows_of_base(
                 &base_place,
                 block,
@@ -710,12 +727,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         let lt = self.temp(bool_ty, expr_span);
 
         // len = len(slice)
-        self.cfg.push_assign(
-            block,
-            source_info,
-            len,
-            Rvalue::Len(slice.into_place(self.tcx, self.typeck_results)),
-        );
+        self.cfg.push_assign(block, source_info, len, Rvalue::Len(slice.into_place(self)));
         // lt = idx < len
         self.cfg.push_assign(
             block,
@@ -795,6 +807,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     }
                     ProjectionElem::Field(..)
                     | ProjectionElem::Downcast(..)
+                    | ProjectionElem::OpaqueCast(..)
                     | ProjectionElem::ConstantIndex { .. }
                     | ProjectionElem::Subslice { .. } => (),
                 }
diff --git a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
index 15f2d17c4e08b..93f76333165a5 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
@@ -321,11 +321,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     let place_builder =
                         unpack!(block = this.as_place_builder(block, &this.thir[*thir_place]));
 
-                    if let Ok(place_builder_resolved) =
-                        place_builder.try_upvars_resolved(this.tcx, this.typeck_results)
-                    {
-                        let mir_place =
-                            place_builder_resolved.into_place(this.tcx, this.typeck_results);
+                    if let Ok(place_builder_resolved) = place_builder.try_upvars_resolved(this) {
+                        let mir_place = place_builder_resolved.into_place(this);
                         this.cfg.push_fake_read(
                             block,
                             this.source_info(this.tcx.hir().span(*hir_id)),
@@ -616,8 +613,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             // by the parent itself. The mutability of the current capture
             // is same as that of the capture in the parent closure.
             PlaceBase::Upvar { .. } => {
-                let enclosing_upvars_resolved =
-                    arg_place_builder.clone().into_place(this.tcx, this.typeck_results);
+                let enclosing_upvars_resolved = arg_place_builder.clone().into_place(this);
 
                 match enclosing_upvars_resolved.as_ref() {
                     PlaceRef {
@@ -654,7 +650,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             Mutability::Mut => BorrowKind::Mut { allow_two_phase_borrow: false },
         };
 
-        let arg_place = arg_place_builder.into_place(this.tcx, this.typeck_results);
+        let arg_place = arg_place_builder.into_place(this);
 
         this.cfg.push_assign(
             block,
diff --git a/compiler/rustc_mir_build/src/build/expr/as_temp.rs b/compiler/rustc_mir_build/src/build/expr/as_temp.rs
index 724b72f8769b8..dac8862647a85 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_temp.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_temp.rs
@@ -23,6 +23,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         ensure_sufficient_stack(|| self.as_temp_inner(block, temp_lifetime, expr, mutability))
     }
 
+    #[instrument(skip(self), level = "debug")]
     fn as_temp_inner(
         &mut self,
         mut block: BasicBlock,
@@ -30,10 +31,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         expr: &Expr<'tcx>,
         mutability: Mutability,
     ) -> BlockAnd<Local> {
-        debug!(
-            "as_temp(block={:?}, temp_lifetime={:?}, expr={:?}, mutability={:?})",
-            block, temp_lifetime, expr, mutability
-        );
         let this = self;
 
         let expr_span = expr.span;
diff --git a/compiler/rustc_mir_build/src/build/expr/into.rs b/compiler/rustc_mir_build/src/build/expr/into.rs
index 017d43d10a9a9..d1ef515b3d29b 100644
--- a/compiler/rustc_mir_build/src/build/expr/into.rs
+++ b/compiler/rustc_mir_build/src/build/expr/into.rs
@@ -15,14 +15,13 @@ use std::iter;
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Compile `expr`, storing the result into `destination`, which
     /// is assumed to be uninitialized.
+    #[instrument(level = "debug", skip(self))]
     pub(crate) fn expr_into_dest(
         &mut self,
         destination: Place<'tcx>,
         mut block: BasicBlock,
         expr: &Expr<'tcx>,
     ) -> BlockAnd<()> {
-        debug!("expr_into_dest(destination={:?}, block={:?}, expr={:?})", destination, block, expr);
-
         // since we frequently have to reference `self` from within a
         // closure, where `self` would be shadowed, it's easier to
         // just use the name `this` uniformly
@@ -366,9 +365,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             None => {
                                 let place_builder = place_builder.clone();
                                 this.consume_by_copy_or_move(
-                                    place_builder
-                                        .field(n, *ty)
-                                        .into_place(this.tcx, this.typeck_results),
+                                    place_builder.field(n, *ty).into_place(this),
                                 )
                             }
                         })
diff --git a/compiler/rustc_mir_build/src/build/matches/mod.rs b/compiler/rustc_mir_build/src/build/matches/mod.rs
index 7067a48b783ec..86ef666eac8d2 100644
--- a/compiler/rustc_mir_build/src/build/matches/mod.rs
+++ b/compiler/rustc_mir_build/src/build/matches/mod.rs
@@ -220,10 +220,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         let cause_matched_place = FakeReadCause::ForMatchedPlace(None);
         let source_info = self.source_info(scrutinee_span);
 
-        if let Ok(scrutinee_builder) =
-            scrutinee_place_builder.clone().try_upvars_resolved(self.tcx, self.typeck_results)
-        {
-            let scrutinee_place = scrutinee_builder.into_place(self.tcx, self.typeck_results);
+        if let Ok(scrutinee_builder) = scrutinee_place_builder.clone().try_upvars_resolved(self) {
+            let scrutinee_place = scrutinee_builder.into_place(self);
             self.cfg.push_fake_read(block, source_info, cause_matched_place, scrutinee_place);
         }
 
@@ -348,12 +346,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     // ```
                     let mut opt_scrutinee_place: Option<(Option<&Place<'tcx>>, Span)> = None;
                     let scrutinee_place: Place<'tcx>;
-                    if let Ok(scrutinee_builder) = scrutinee_place_builder
-                        .clone()
-                        .try_upvars_resolved(this.tcx, this.typeck_results)
+                    if let Ok(scrutinee_builder) =
+                        scrutinee_place_builder.clone().try_upvars_resolved(this)
                     {
-                        scrutinee_place =
-                            scrutinee_builder.into_place(this.tcx, this.typeck_results);
+                        scrutinee_place = scrutinee_builder.into_place(this);
                         opt_scrutinee_place = Some((Some(&scrutinee_place), scrutinee_span));
                     }
                     let scope = this.declare_bindings(
@@ -602,12 +598,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             while let Some(next) = {
                 for binding in &candidate_ref.bindings {
                     let local = self.var_local_id(binding.var_id, OutsideGuard);
-
-                    let Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::Var(
-                        VarBindingForm { opt_match_place: Some((ref mut match_place, _)), .. },
-                    )))) = self.local_decls[local].local_info else {
-                        bug!("Let binding to non-user variable.")
-                    };
                     // `try_upvars_resolved` may fail if it is unable to resolve the given
                     // `PlaceBuilder` inside a closure. In this case, we don't want to include
                     // a scrutinee place. `scrutinee_place_builder` will fail for destructured
@@ -622,10 +612,15 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     //    let (v1, v2) = foo;
                     // };
                     // ```
-                    if let Ok(match_pair_resolved) =
-                        initializer.clone().try_upvars_resolved(self.tcx, self.typeck_results)
-                    {
-                        let place = match_pair_resolved.into_place(self.tcx, self.typeck_results);
+                    if let Ok(match_pair_resolved) = initializer.clone().try_upvars_resolved(self) {
+                        let place = match_pair_resolved.into_place(self);
+
+                        let Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::Var(
+                            VarBindingForm { opt_match_place: Some((ref mut match_place, _)), .. },
+                        )))) = self.local_decls[local].local_info else {
+                            bug!("Let binding to non-user variable.")
+                        };
+
                         *match_place = Some(place);
                     }
                 }
@@ -654,6 +649,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// scope for the bindings in these patterns, if such a scope had to be
     /// created. NOTE: Declaring the bindings should always be done in their
     /// drop scope.
+    #[instrument(skip(self), level = "debug")]
     pub(crate) fn declare_bindings(
         &mut self,
         mut visibility_scope: Option<SourceScope>,
@@ -662,7 +658,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         has_guard: ArmHasGuard,
         opt_match_place: Option<(Option<&Place<'tcx>>, Span)>,
     ) -> Option<SourceScope> {
-        debug!("declare_bindings: pattern={:?}", pattern);
         self.visit_primary_bindings(
             &pattern,
             UserTypeProjections::none(),
@@ -872,7 +867,7 @@ impl<'tcx, 'pat> Candidate<'pat, 'tcx> {
         Candidate {
             span: pattern.span,
             has_guard,
-            match_pairs: smallvec![MatchPair { place, pattern }],
+            match_pairs: smallvec![MatchPair::new(place, pattern)],
             bindings: Vec::new(),
             ascriptions: Vec::new(),
             subcandidates: Vec::new(),
@@ -1048,6 +1043,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// if `x.0` matches `false` (for the third arm). In the (impossible at
     /// runtime) case when `x.0` is now `true`, we branch to
     /// `otherwise_block`.
+    #[instrument(skip(self, fake_borrows), level = "debug")]
     fn match_candidates<'pat>(
         &mut self,
         span: Span,
@@ -1057,11 +1053,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         candidates: &mut [&mut Candidate<'pat, 'tcx>],
         fake_borrows: &mut Option<FxIndexSet<Place<'tcx>>>,
     ) {
-        debug!(
-            "matched_candidate(span={:?}, candidates={:?}, start_block={:?}, otherwise_block={:?})",
-            span, candidates, start_block, otherwise_block,
-        );
-
         // Start by simplifying candidates. Once this process is complete, all
         // the match pairs which remain require some form of test, whether it
         // be a switch or pattern comparison.
@@ -1380,6 +1371,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         )
     }
 
+    #[instrument(
+        skip(self, otherwise, or_span, place, fake_borrows, candidate, pats),
+        level = "debug"
+    )]
     fn test_or_pattern<'pat>(
         &mut self,
         candidate: &mut Candidate<'pat, 'tcx>,
@@ -1389,7 +1384,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         place: PlaceBuilder<'tcx>,
         fake_borrows: &mut Option<FxIndexSet<Place<'tcx>>>,
     ) {
-        debug!("test_or_pattern:\ncandidate={:#?}\npats={:#?}", candidate, pats);
+        debug!("candidate={:#?}\npats={:#?}", candidate, pats);
         let mut or_candidates: Vec<_> = pats
             .iter()
             .map(|pat| Candidate::new(place.clone(), pat, candidate.has_guard))
@@ -1605,9 +1600,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
         // Insert a Shallow borrow of any places that is switched on.
         if let Some(fb) = fake_borrows && let Ok(match_place_resolved) =
-            match_place.clone().try_upvars_resolved(self.tcx, self.typeck_results)
+            match_place.clone().try_upvars_resolved(self)
         {
-            let resolved_place = match_place_resolved.into_place(self.tcx, self.typeck_results);
+            let resolved_place = match_place_resolved.into_place(self);
             fb.insert(resolved_place);
         }
 
@@ -1634,9 +1629,14 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             candidates = rest;
         }
         // at least the first candidate ought to be tested
-        assert!(total_candidate_count > candidates.len());
-        debug!("test_candidates: tested_candidates: {}", total_candidate_count - candidates.len());
-        debug!("test_candidates: untested_candidates: {}", candidates.len());
+        assert!(
+            total_candidate_count > candidates.len(),
+            "{}, {:#?}",
+            total_candidate_count,
+            candidates
+        );
+        debug!("tested_candidates: {}", total_candidate_count - candidates.len());
+        debug!("untested_candidates: {}", candidates.len());
 
         // HACK(matthewjasper) This is a closure so that we can let the test
         // create its blocks before the rest of the match. This currently
@@ -1794,10 +1794,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         );
         let mut opt_expr_place: Option<(Option<&Place<'tcx>>, Span)> = None;
         let expr_place: Place<'tcx>;
-        if let Ok(expr_builder) =
-            expr_place_builder.try_upvars_resolved(self.tcx, self.typeck_results)
-        {
-            expr_place = expr_builder.into_place(self.tcx, self.typeck_results);
+        if let Ok(expr_builder) = expr_place_builder.try_upvars_resolved(self) {
+            expr_place = expr_builder.into_place(self);
             opt_expr_place = Some((Some(&expr_place), expr_span));
         }
         let otherwise_post_guard_block = otherwise_candidate.pre_binding_block.unwrap();
@@ -2195,6 +2193,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// first local is a binding for occurrences of `var` in the guard, which
     /// will have type `&T`. The second local is a binding for occurrences of
     /// `var` in the arm body, which will have type `T`.
+    #[instrument(skip(self), level = "debug")]
     fn declare_binding(
         &mut self,
         source_info: SourceInfo,
@@ -2209,19 +2208,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         opt_match_place: Option<(Option<Place<'tcx>>, Span)>,
         pat_span: Span,
     ) {
-        debug!(
-            "declare_binding(var_id={:?}, name={:?}, mode={:?}, var_ty={:?}, \
-             visibility_scope={:?}, source_info={:?})",
-            var_id, name, mode, var_ty, visibility_scope, source_info
-        );
-
         let tcx = self.tcx;
         let debug_source_info = SourceInfo { span: source_info.span, scope: visibility_scope };
         let binding_mode = match mode {
             BindingMode::ByValue => ty::BindingMode::BindByValue(mutability),
             BindingMode::ByRef(_) => ty::BindingMode::BindByReference(mutability),
         };
-        debug!("declare_binding: user_ty={:?}", user_ty);
         let local = LocalDecl::<'tcx> {
             mutability,
             ty: var_ty,
@@ -2271,7 +2263,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         } else {
             LocalsForNode::One(for_arm_body)
         };
-        debug!("declare_binding: vars={:?}", locals);
+        debug!(?locals);
         self.var_indices.insert(var_id, locals);
     }
 
diff --git a/compiler/rustc_mir_build/src/build/matches/simplify.rs b/compiler/rustc_mir_build/src/build/matches/simplify.rs
index c6298904140c3..6fa817da28a3c 100644
--- a/compiler/rustc_mir_build/src/build/matches/simplify.rs
+++ b/compiler/rustc_mir_build/src/build/matches/simplify.rs
@@ -37,12 +37,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     ///
     /// only generates a single switch. If this happens this method returns
     /// `true`.
+    #[instrument(skip(self, candidate), level = "debug")]
     pub(super) fn simplify_candidate<'pat>(
         &mut self,
         candidate: &mut Candidate<'pat, 'tcx>,
     ) -> bool {
         // repeatedly simplify match pairs until fixed point is reached
-        debug!(?candidate, "simplify_candidate");
+        debug!("{:#?}", candidate);
 
         // existing_bindings and new_bindings exists to keep the semantics in order.
         // Reversing the binding order for bindings after `@` changes the binding order in places
@@ -155,12 +156,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 ascription: thir::Ascription { ref annotation, variance },
             } => {
                 // Apply the type ascription to the value at `match_pair.place`, which is the
-                if let Ok(place_resolved) =
-                    match_pair.place.clone().try_upvars_resolved(self.tcx, self.typeck_results)
-                {
+                if let Ok(place_resolved) = match_pair.place.clone().try_upvars_resolved(self) {
                     candidate.ascriptions.push(Ascription {
                         annotation: annotation.clone(),
-                        source: place_resolved.into_place(self.tcx, self.typeck_results),
+                        source: place_resolved.into_place(self),
                         variance,
                     });
                 }
@@ -184,12 +183,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 ref subpattern,
                 is_primary: _,
             } => {
-                if let Ok(place_resolved) =
-                    match_pair.place.clone().try_upvars_resolved(self.tcx, self.typeck_results)
-                {
+                if let Ok(place_resolved) = match_pair.place.clone().try_upvars_resolved(self) {
                     candidate.bindings.push(Binding {
                         span: match_pair.pattern.span,
-                        source: place_resolved.into_place(self.tcx, self.typeck_results),
+                        source: place_resolved.into_place(self),
                         var_id: var,
                         binding_mode: mode,
                     });
diff --git a/compiler/rustc_mir_build/src/build/matches/test.rs b/compiler/rustc_mir_build/src/build/matches/test.rs
index 598da80c574af..63acd731db7c9 100644
--- a/compiler/rustc_mir_build/src/build/matches/test.rs
+++ b/compiler/rustc_mir_build/src/build/matches/test.rs
@@ -144,6 +144,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         }
     }
 
+    #[instrument(skip(self, make_target_blocks, place_builder), level = "debug")]
     pub(super) fn perform_test(
         &mut self,
         match_start_span: Span,
@@ -153,21 +154,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         test: &Test<'tcx>,
         make_target_blocks: impl FnOnce(&mut Self) -> Vec<BasicBlock>,
     ) {
-        let place: Place<'tcx>;
-        if let Ok(test_place_builder) =
-            place_builder.try_upvars_resolved(self.tcx, self.typeck_results)
-        {
-            place = test_place_builder.into_place(self.tcx, self.typeck_results);
-        } else {
-            return;
-        }
-        debug!(
-            "perform_test({:?}, {:?}: {:?}, {:?})",
-            block,
-            place,
-            place.ty(&self.local_decls, self.tcx),
-            test
-        );
+        let place = place_builder.into_place(self);
+        let place_ty = place.ty(&self.local_decls, self.tcx);
+        debug!(?place, ?place_ty,);
 
         let source_info = self.source_info(test.span);
         match test.kind {
@@ -735,9 +724,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         // So, if we have a match-pattern like `x @ Enum::Variant(P1, P2)`,
         // we want to create a set of derived match-patterns like
         // `(x as Variant).0 @ P1` and `(x as Variant).1 @ P1`.
-        let elem =
-            ProjectionElem::Downcast(Some(adt_def.variant(variant_index).name), variant_index);
-        let downcast_place = match_pair.place.project(elem); // `(x as Variant)`
+        let downcast_place = match_pair.place.downcast(adt_def, variant_index); // `(x as Variant)`
         let consequent_match_pairs = subpatterns.iter().map(|subpattern| {
             // e.g., `(x as Variant).0`
             let place = downcast_place.clone().field(subpattern.field, subpattern.pattern.ty);
diff --git a/compiler/rustc_mir_build/src/build/matches/util.rs b/compiler/rustc_mir_build/src/build/matches/util.rs
index 9a1e98d3bb18d..4a7edc517f4e4 100644
--- a/compiler/rustc_mir_build/src/build/matches/util.rs
+++ b/compiler/rustc_mir_build/src/build/matches/util.rs
@@ -31,21 +31,15 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         suffix: &'pat [Pat<'tcx>],
     ) {
         let tcx = self.tcx;
-        let (min_length, exact_size) = if let Ok(place_resolved) =
-            place.clone().try_upvars_resolved(tcx, self.typeck_results)
-        {
-            match place_resolved
-                .into_place(tcx, self.typeck_results)
-                .ty(&self.local_decls, tcx)
-                .ty
-                .kind()
-            {
-                ty::Array(_, length) => (length.eval_usize(tcx, self.param_env), true),
-                _ => ((prefix.len() + suffix.len()).try_into().unwrap(), false),
-            }
-        } else {
-            ((prefix.len() + suffix.len()).try_into().unwrap(), false)
-        };
+        let (min_length, exact_size) =
+            if let Ok(place_resolved) = place.clone().try_upvars_resolved(self) {
+                match place_resolved.into_place(self).ty(&self.local_decls, tcx).ty.kind() {
+                    ty::Array(_, length) => (length.eval_usize(tcx, self.param_env), true),
+                    _ => ((prefix.len() + suffix.len()).try_into().unwrap(), false),
+                }
+            } else {
+                ((prefix.len() + suffix.len()).try_into().unwrap(), false)
+            };
 
         match_pairs.extend(prefix.iter().enumerate().map(|(idx, subpattern)| {
             let elem =
@@ -100,10 +94,14 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 }
 
 impl<'pat, 'tcx> MatchPair<'pat, 'tcx> {
-    pub(crate) fn new(
+    pub(in crate::build) fn new(
         place: PlaceBuilder<'tcx>,
         pattern: &'pat Pat<'tcx>,
     ) -> MatchPair<'pat, 'tcx> {
+        // Force the place type to the pattern's type.
+        // FIXME(oli-obk): only do this when we don't already know the place type.
+        // FIXME(oli-obk): can we use this to simplify slice/array pattern hacks?
+        let place = place.project(ProjectionElem::OpaqueCast(pattern.ty));
         MatchPair { place, pattern }
     }
 }
diff --git a/compiler/rustc_mir_build/src/build/scope.rs b/compiler/rustc_mir_build/src/build/scope.rs
index b9fd8c50e6a04..ab37c4802852a 100644
--- a/compiler/rustc_mir_build/src/build/scope.rs
+++ b/compiler/rustc_mir_build/src/build/scope.rs
@@ -553,6 +553,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
     /// Convenience wrapper that pushes a scope and then executes `f`
     /// to build its contents, popping the scope afterwards.
+    #[instrument(skip(self, f), level = "debug")]
     pub(crate) fn in_scope<F, R>(
         &mut self,
         region_scope: (region::Scope, SourceInfo),
@@ -562,7 +563,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     where
         F: FnOnce(&mut Builder<'a, 'tcx>) -> BlockAnd<R>,
     {
-        debug!("in_scope(region_scope={:?})", region_scope);
         let source_scope = self.source_scope;
         let tcx = self.tcx;
         if let LintLevel::Explicit(current_hir_id) = lint_level {
@@ -589,7 +589,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         let rv = unpack!(block = f(self));
         unpack!(block = self.pop_scope(region_scope, block));
         self.source_scope = source_scope;
-        debug!("in_scope: exiting region_scope={:?} block={:?}", region_scope, block);
+        debug!(?block);
         block.and(rv)
     }
 
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 4eb3607e9cca0..05da33caa91bd 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -48,6 +48,8 @@ impl<'tcx> Cx<'tcx> {
             _ => None,
         };
 
+        trace!(?expr.ty);
+
         // Now apply adjustments, if any.
         for adjustment in self.typeck_results.expr_adjustments(hir_expr) {
             trace!(?expr, ?adjustment);
@@ -56,6 +58,8 @@ impl<'tcx> Cx<'tcx> {
                 self.apply_adjustment(hir_expr, expr, adjustment, adjustment_span.unwrap_or(span));
         }
 
+        trace!(?expr.ty, "after adjustments");
+
         // Next, wrap this up in the expr's scope.
         expr = Expr {
             temp_lifetime,
diff --git a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
index 60db98073a3b9..c0fd19cf71c31 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
@@ -1202,35 +1202,32 @@ impl<'p, 'tcx> Fields<'p, 'tcx> {
 
     /// Creates a new list of wildcard fields for a given constructor. The result must have a
     /// length of `constructor.arity()`.
-    pub(super) fn wildcards(
-        cx: &MatchCheckCtxt<'p, 'tcx>,
-        ty: Ty<'tcx>,
-        constructor: &Constructor<'tcx>,
-    ) -> Self {
+    #[instrument(level = "trace")]
+    pub(super) fn wildcards(pcx: PatCtxt<'_, 'p, 'tcx>, constructor: &Constructor<'tcx>) -> Self {
         let ret = match constructor {
-            Single | Variant(_) => match ty.kind() {
-                ty::Tuple(fs) => Fields::wildcards_from_tys(cx, fs.iter()),
-                ty::Ref(_, rty, _) => Fields::wildcards_from_tys(cx, once(*rty)),
+            Single | Variant(_) => match pcx.ty.kind() {
+                ty::Tuple(fs) => Fields::wildcards_from_tys(pcx.cx, fs.iter()),
+                ty::Ref(_, rty, _) => Fields::wildcards_from_tys(pcx.cx, once(*rty)),
                 ty::Adt(adt, substs) => {
                     if adt.is_box() {
                         // The only legal patterns of type `Box` (outside `std`) are `_` and box
                         // patterns. If we're here we can assume this is a box pattern.
-                        Fields::wildcards_from_tys(cx, once(substs.type_at(0)))
+                        Fields::wildcards_from_tys(pcx.cx, once(substs.type_at(0)))
                     } else {
                         let variant = &adt.variant(constructor.variant_index_for_adt(*adt));
-                        let tys = Fields::list_variant_nonhidden_fields(cx, ty, variant)
+                        let tys = Fields::list_variant_nonhidden_fields(pcx.cx, pcx.ty, variant)
                             .map(|(_, ty)| ty);
-                        Fields::wildcards_from_tys(cx, tys)
+                        Fields::wildcards_from_tys(pcx.cx, tys)
                     }
                 }
-                _ => bug!("Unexpected type for `Single` constructor: {:?}", ty),
+                _ => bug!("Unexpected type for `Single` constructor: {:?}", pcx),
             },
-            Slice(slice) => match *ty.kind() {
+            Slice(slice) => match *pcx.ty.kind() {
                 ty::Slice(ty) | ty::Array(ty, _) => {
                     let arity = slice.arity();
-                    Fields::wildcards_from_tys(cx, (0..arity).map(|_| ty))
+                    Fields::wildcards_from_tys(pcx.cx, (0..arity).map(|_| ty))
                 }
-                _ => bug!("bad slice pattern {:?} {:?}", constructor, ty),
+                _ => bug!("bad slice pattern {:?} {:?}", constructor, pcx),
             },
             Str(..)
             | FloatRange(..)
@@ -1243,7 +1240,7 @@ impl<'p, 'tcx> Fields<'p, 'tcx> {
                 bug!("called `Fields::wildcards` on an `Or` ctor")
             }
         };
-        debug!("Fields::wildcards({:?}, {:?}) = {:#?}", constructor, ty, ret);
+        debug!(?ret);
         ret
     }
 
@@ -1286,7 +1283,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
     /// For example, if `ctor` is a `Constructor::Variant` for `Option::Some`, we get the pattern
     /// `Some(_)`.
     pub(super) fn wild_from_ctor(pcx: PatCtxt<'_, 'p, 'tcx>, ctor: Constructor<'tcx>) -> Self {
-        let fields = Fields::wildcards(pcx.cx, pcx.ty, &ctor);
+        let fields = Fields::wildcards(pcx, &ctor);
         DeconstructedPat::new(ctor, fields, pcx.ty, DUMMY_SP)
     }
 
@@ -1553,13 +1550,13 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
     /// `other_ctor` can be different from `self.ctor`, but must be covered by it.
     pub(super) fn specialize<'a>(
         &'a self,
-        cx: &MatchCheckCtxt<'p, 'tcx>,
+        pcx: PatCtxt<'_, 'p, 'tcx>,
         other_ctor: &Constructor<'tcx>,
     ) -> SmallVec<[&'p DeconstructedPat<'p, 'tcx>; 2]> {
         match (&self.ctor, other_ctor) {
             (Wildcard, _) => {
                 // We return a wildcard for each field of `other_ctor`.
-                Fields::wildcards(cx, self.ty, other_ctor).iter_patterns().collect()
+                Fields::wildcards(pcx, other_ctor).iter_patterns().collect()
             }
             (Slice(self_slice), Slice(other_slice))
                 if self_slice.arity() != other_slice.arity() =>
@@ -1578,7 +1575,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
                         let prefix = &self.fields.fields[..prefix];
                         let suffix = &self.fields.fields[self_slice.arity() - suffix..];
                         let wildcard: &_ =
-                            cx.pattern_arena.alloc(DeconstructedPat::wildcard(inner_ty));
+                            pcx.cx.pattern_arena.alloc(DeconstructedPat::wildcard(inner_ty));
                         let extra_wildcards = other_slice.arity() - self_slice.arity();
                         let extra_wildcards = (0..extra_wildcards).map(|_| wildcard);
                         prefix.iter().chain(extra_wildcards).chain(suffix).collect()
diff --git a/compiler/rustc_mir_build/src/thir/pattern/mod.rs b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
index a13748a2d474a..7d22f7b69d862 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
@@ -196,6 +196,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         }
     }
 
+    #[instrument(skip(self), level = "debug")]
     fn lower_pattern_unadjusted(&mut self, pat: &'tcx hir::Pat<'tcx>) -> Pat<'tcx> {
         let mut ty = self.typeck_results.node_type(pat.hir_id);
 
diff --git a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
index 9e7a267ecbd7f..f27ec22a8dee2 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
@@ -411,12 +411,12 @@ impl<'p, 'tcx> PatStack<'p, 'tcx> {
     /// This is roughly the inverse of `Constructor::apply`.
     fn pop_head_constructor(
         &self,
-        cx: &MatchCheckCtxt<'p, 'tcx>,
+        pcx: PatCtxt<'_, 'p, 'tcx>,
         ctor: &Constructor<'tcx>,
     ) -> PatStack<'p, 'tcx> {
         // We pop the head pattern and push the new fields extracted from the arguments of
         // `self.head()`.
-        let mut new_fields: SmallVec<[_; 2]> = self.head().specialize(cx, ctor);
+        let mut new_fields: SmallVec<[_; 2]> = self.head().specialize(pcx, ctor);
         new_fields.extend_from_slice(&self.pats[1..]);
         PatStack::from_vec(new_fields)
     }
@@ -475,7 +475,7 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> {
         let mut matrix = Matrix::empty();
         for row in &self.patterns {
             if ctor.is_covered_by(pcx, row.head().ctor()) {
-                let new_row = row.pop_head_constructor(pcx.cx, ctor);
+                let new_row = row.pop_head_constructor(pcx, ctor);
                 matrix.push(new_row);
             }
         }
@@ -786,7 +786,7 @@ fn is_useful<'p, 'tcx>(
     is_under_guard: bool,
     is_top_level: bool,
 ) -> Usefulness<'p, 'tcx> {
-    debug!("matrix,v={:?}{:?}", matrix, v);
+    debug!(?matrix, ?v);
     let Matrix { patterns: rows, .. } = matrix;
 
     // The base case. We are pattern-matching on () and the return value is
@@ -806,11 +806,6 @@ fn is_useful<'p, 'tcx>(
 
     debug_assert!(rows.iter().all(|r| r.len() == v.len()));
 
-    let ty = v.head().ty();
-    let is_non_exhaustive = cx.is_foreign_non_exhaustive_enum(ty);
-    debug!("v.head: {:?}, v.span: {:?}", v.head(), v.head().span());
-    let pcx = PatCtxt { cx, ty, span: v.head().span(), is_top_level, is_non_exhaustive };
-
     // If the first pattern is an or-pattern, expand it.
     let mut ret = Usefulness::new_not_useful(witness_preference);
     if v.head().is_or_pat() {
@@ -832,6 +827,19 @@ fn is_useful<'p, 'tcx>(
             }
         }
     } else {
+        let mut ty = v.head().ty();
+
+        // Opaque types can't get destructured/split, but the patterns can
+        // actually hint at hidden types, so we use the patterns' types instead.
+        if let ty::Opaque(..) = v.head().ty().kind() {
+            if let Some(row) = rows.first() {
+                ty = row.head().ty();
+            }
+        }
+        let is_non_exhaustive = cx.is_foreign_non_exhaustive_enum(ty);
+        debug!("v.head: {:?}, v.span: {:?}", v.head(), v.head().span());
+        let pcx = PatCtxt { cx, ty, span: v.head().span(), is_top_level, is_non_exhaustive };
+
         let v_ctor = v.head().ctor();
         debug!(?v_ctor);
         if let Constructor::IntRange(ctor_range) = &v_ctor {
@@ -853,7 +861,7 @@ fn is_useful<'p, 'tcx>(
             debug!("specialize({:?})", ctor);
             // We cache the result of `Fields::wildcards` because it is used a lot.
             let spec_matrix = start_matrix.specialize_constructor(pcx, &ctor);
-            let v = v.pop_head_constructor(cx, &ctor);
+            let v = v.pop_head_constructor(pcx, &ctor);
             let usefulness = ensure_sufficient_stack(|| {
                 is_useful(cx, &spec_matrix, &v, witness_preference, hir_id, is_under_guard, false)
             });
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs b/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs
index 28936274baafa..7806e8f45d3ad 100644
--- a/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs
+++ b/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs
@@ -48,6 +48,7 @@ impl<'tcx> Lift for PlaceElem<'tcx> {
         match *self {
             ProjectionElem::Deref => ProjectionElem::Deref,
             ProjectionElem::Field(f, ty) => ProjectionElem::Field(f, ty.lift()),
+            ProjectionElem::OpaqueCast(ty) => ProjectionElem::OpaqueCast(ty.lift()),
             ProjectionElem::Index(ref i) => ProjectionElem::Index(i.lift()),
             ProjectionElem::Subslice { from, to, from_end } => {
                 ProjectionElem::Subslice { from, to, from_end }
diff --git a/compiler/rustc_mir_transform/src/add_retag.rs b/compiler/rustc_mir_transform/src/add_retag.rs
index b91ae083cf594..86327ade94b8a 100644
--- a/compiler/rustc_mir_transform/src/add_retag.rs
+++ b/compiler/rustc_mir_transform/src/add_retag.rs
@@ -28,6 +28,7 @@ fn is_stable(place: PlaceRef<'_>) -> bool {
             ProjectionElem::Field { .. } |
             ProjectionElem::ConstantIndex { .. } |
             ProjectionElem::Subslice { .. } |
+            ProjectionElem::OpaqueCast { .. } |
             ProjectionElem::Downcast { .. } => true,
         }
     })
diff --git a/compiler/rustc_passes/Cargo.toml b/compiler/rustc_passes/Cargo.toml
index 676812db59ae5..faa9c493d8875 100644
--- a/compiler/rustc_passes/Cargo.toml
+++ b/compiler/rustc_passes/Cargo.toml
@@ -15,6 +15,7 @@ rustc_hir = { path = "../rustc_hir" }
 rustc_index = { path = "../rustc_index" }
 rustc_session = { path = "../rustc_session" }
 rustc_target = { path = "../rustc_target" }
+rustc_macros = { path = "../rustc_macros" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index e626a1e4ed101..d96e7d3efe83d 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -4,9 +4,10 @@
 //! conflicts between multiple such attributes attached to the same
 //! item.
 
+use crate::errors;
 use rustc_ast::{ast, AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem};
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::{pluralize, struct_span_err, Applicability, MultiSpan};
+use rustc_errors::{fluent, pluralize, struct_span_err, Applicability, MultiSpan};
 use rustc_expand::base::resolve_path;
 use rustc_feature::{AttributeDuplicates, AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
 use rustc_hir as hir;
@@ -175,16 +176,20 @@ impl CheckAttrVisitor<'_> {
                 if let Some(BuiltinAttribute { type_: AttributeType::CrateLevel, .. }) =
                     attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name))
                 {
-                    self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-                        let msg = match attr.style {
-                            ast::AttrStyle::Outer => {
-                                "crate-level attribute should be an inner attribute: add an exclamation \
-                                 mark: `#![foo]`"
-                            }
-                            ast::AttrStyle::Inner => "crate-level attribute should be in the root module",
-                        };
-                        lint.build(msg).emit();
-                    });
+                    match attr.style {
+                        ast::AttrStyle::Outer => self.tcx.emit_spanned_lint(
+                            UNUSED_ATTRIBUTES,
+                            hir_id,
+                            attr.span,
+                            errors::OuterCrateLevelAttr,
+                        ),
+                        ast::AttrStyle::Inner => self.tcx.emit_spanned_lint(
+                            UNUSED_ATTRIBUTES,
+                            hir_id,
+                            attr.span,
+                            errors::InnerCrateLevelAttr,
+                        ),
+                    }
                 }
             }
 
@@ -209,37 +214,21 @@ impl CheckAttrVisitor<'_> {
     }
 
     fn inline_attr_str_error_with_macro_def(&self, hir_id: HirId, attr: &Attribute, sym: &str) {
-        self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-            lint.build(&format!(
-                "`#[{sym}]` is ignored on struct fields, match arms and macro defs",
-            ))
-            .warn(
-                "this was previously accepted by the compiler but is \
-                 being phased out; it will become a hard error in \
-                 a future release!",
-            )
-            .note(
-                "see issue #80564 <https://github.com/rust-lang/rust/issues/80564> \
-                 for more information",
-            )
-            .emit();
-        });
+        self.tcx.emit_spanned_lint(
+            UNUSED_ATTRIBUTES,
+            hir_id,
+            attr.span,
+            errors::IgnoredAttrWithMacro { sym },
+        );
     }
 
     fn inline_attr_str_error_without_macro_def(&self, hir_id: HirId, attr: &Attribute, sym: &str) {
-        self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-            lint.build(&format!("`#[{sym}]` is ignored on struct fields and match arms"))
-                .warn(
-                    "this was previously accepted by the compiler but is \
-                 being phased out; it will become a hard error in \
-                 a future release!",
-                )
-                .note(
-                    "see issue #80564 <https://github.com/rust-lang/rust/issues/80564> \
-                 for more information",
-                )
-                .emit();
-        });
+        self.tcx.emit_spanned_lint(
+            UNUSED_ATTRIBUTES,
+            hir_id,
+            attr.span,
+            errors::IgnoredAttr { sym },
+        );
     }
 
     /// Checks if an `#[inline]` is applied to a function or a closure. Returns `true` if valid.
@@ -249,9 +238,12 @@ impl CheckAttrVisitor<'_> {
             | Target::Closure
             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
             Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => {
-                self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-                    lint.build("`#[inline]` is ignored on function prototypes").emit();
-                });
+                self.tcx.emit_spanned_lint(
+                    UNUSED_ATTRIBUTES,
+                    hir_id,
+                    attr.span,
+                    errors::IgnoredInlineAttrFnProto,
+                );
                 true
             }
             // FIXME(#65833): We permit associated consts to have an `#[inline]` attribute with
@@ -259,19 +251,12 @@ impl CheckAttrVisitor<'_> {
             // accidentally, to to be compatible with crates depending on them, we can't throw an
             // error here.
             Target::AssocConst => {
-                self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-                    lint.build("`#[inline]` is ignored on constants")
-                        .warn(
-                            "this was previously accepted by the compiler but is \
-                             being phased out; it will become a hard error in \
-                             a future release!",
-                        )
-                        .note(
-                            "see issue #65833 <https://github.com/rust-lang/rust/issues/65833> \
-                             for more information",
-                        )
-                        .emit();
-                });
+                self.tcx.emit_spanned_lint(
+                    UNUSED_ATTRIBUTES,
+                    hir_id,
+                    attr.span,
+                    errors::IgnoredInlineAttrConstants,
+                );
                 true
             }
             // FIXME(#80564): Same for fields, arms, and macro defs
@@ -280,14 +265,10 @@ impl CheckAttrVisitor<'_> {
                 true
             }
             _ => {
-                struct_span_err!(
-                    self.tcx.sess,
-                    attr.span,
-                    E0518,
-                    "attribute should be applied to function or closure",
-                )
-                .span_label(span, "not a function or closure")
-                .emit();
+                self.tcx.sess.emit_err(errors::InlineNotFnOrClosure {
+                    attr_span: attr.span,
+                    defn_span: span,
+                });
                 false
             }
         }
@@ -309,36 +290,40 @@ impl CheckAttrVisitor<'_> {
 
             // function prototypes can't be covered
             Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => {
-                self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-                    lint.build("`#[no_coverage]` is ignored on function prototypes").emit();
-                });
+                self.tcx.emit_spanned_lint(
+                    UNUSED_ATTRIBUTES,
+                    hir_id,
+                    attr.span,
+                    errors::IgnoredNoCoverageFnProto,
+                );
                 true
             }
 
             Target::Mod | Target::ForeignMod | Target::Impl | Target::Trait => {
-                self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-                    lint.build("`#[no_coverage]` does not propagate into items and must be applied to the contained functions directly").emit();
-                });
+                self.tcx.emit_spanned_lint(
+                    UNUSED_ATTRIBUTES,
+                    hir_id,
+                    attr.span,
+                    errors::IgnoredNoCoveragePropagate,
+                );
                 true
             }
 
             Target::Expression | Target::Statement | Target::Arm => {
-                self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-                    lint.build("`#[no_coverage]` may only be applied to function definitions")
-                        .emit();
-                });
+                self.tcx.emit_spanned_lint(
+                    UNUSED_ATTRIBUTES,
+                    hir_id,
+                    attr.span,
+                    errors::IgnoredNoCoverageFnDefn,
+                );
                 true
             }
 
             _ => {
-                struct_span_err!(
-                    self.tcx.sess,
-                    attr.span,
-                    E0788,
-                    "`#[no_coverage]` must be applied to coverable code",
-                )
-                .span_label(span, "not coverable code")
-                .emit();
+                self.tcx.sess.emit_err(errors::IgnoredNoCoverageNotCoverable {
+                    attr_span: attr.span,
+                    defn_span: span,
+                });
                 false
             }
         }
@@ -389,14 +374,10 @@ impl CheckAttrVisitor<'_> {
                 true
             }
             _ => {
-                self.tcx
-                    .sess
-                    .struct_span_err(
-                        attr.span,
-                        "attribute should be applied to a function definition",
-                    )
-                    .span_label(span, "not a function definition")
-                    .emit();
+                self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
+                    attr_span: attr.span,
+                    defn_span: span,
+                });
                 false
             }
         }
@@ -408,14 +389,10 @@ impl CheckAttrVisitor<'_> {
             Target::Fn
             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
             _ => {
-                self.tcx
-                    .sess
-                    .struct_span_err(
-                        attr.span,
-                        "attribute should be applied to a function definition",
-                    )
-                    .span_label(span, "not a function definition")
-                    .emit();
+                self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
+                    attr_span: attr.span,
+                    defn_span: span,
+                });
                 false
             }
         }
@@ -432,13 +409,7 @@ impl CheckAttrVisitor<'_> {
     ) -> bool {
         match target {
             _ if attrs.iter().any(|attr| attr.has_name(sym::naked)) => {
-                struct_span_err!(
-                    self.tcx.sess,
-                    attr_span,
-                    E0736,
-                    "cannot use `#[track_caller]` with `#[naked]`",
-                )
-                .emit();
+                self.tcx.sess.emit_err(errors::NakedTrackedCaller { attr_span });
                 false
             }
             Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => true,
@@ -453,14 +424,9 @@ impl CheckAttrVisitor<'_> {
                 true
             }
             _ => {
-                struct_span_err!(
-                    self.tcx.sess,
-                    attr_span,
-                    E0739,
-                    "attribute should be applied to function"
-                )
-                .span_label(span, "not a function")
-                .emit();
+                self.tcx
+                    .sess
+                    .emit_err(errors::TrackedCallerWrongLocation { attr_span, defn_span: span });
                 false
             }
         }
@@ -485,14 +451,10 @@ impl CheckAttrVisitor<'_> {
                 true
             }
             _ => {
-                struct_span_err!(
-                    self.tcx.sess,
-                    attr.span,
-                    E0701,
-                    "attribute can only be applied to a struct or enum"
-                )
-                .span_label(span, "not a struct or enum")
-                .emit();
+                self.tcx.sess.emit_err(errors::NonExhaustiveWrongLocation {
+                    attr_span: attr.span,
+                    defn_span: span,
+                });
                 false
             }
         }
@@ -511,11 +473,10 @@ impl CheckAttrVisitor<'_> {
                 true
             }
             _ => {
-                self.tcx
-                    .sess
-                    .struct_span_err(attr.span, "attribute can only be applied to a trait")
-                    .span_label(span, "not a trait")
-                    .emit();
+                self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToTrait {
+                    attr_span: attr.span,
+                    defn_span: span,
+                });
                 false
             }
         }
@@ -531,11 +492,10 @@ impl CheckAttrVisitor<'_> {
         match target {
             Target::Trait => true,
             _ => {
-                self.tcx
-                    .sess
-                    .struct_span_err(attr.span, "attribute can only be applied to a trait")
-                    .span_label(span, "not a trait")
-                    .emit();
+                self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToTrait {
+                    attr_span: attr.span,
+                    defn_span: span,
+                });
                 false
             }
         }
@@ -555,16 +515,12 @@ impl CheckAttrVisitor<'_> {
             // FIXME: #[target_feature] was previously erroneously allowed on statements and some
             // crates used this, so only emit a warning.
             Target::Statement => {
-                self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-                    lint.build("attribute should be applied to a function")
-                        .warn(
-                            "this was previously accepted by the compiler but is \
-                             being phased out; it will become a hard error in \
-                             a future release!",
-                        )
-                        .span_label(span, "not a function")
-                        .emit();
-                });
+                self.tcx.emit_spanned_lint(
+                    UNUSED_ATTRIBUTES,
+                    hir_id,
+                    attr.span,
+                    errors::TargetFeatureOnStatement,
+                );
                 true
             }
             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
@@ -576,11 +532,10 @@ impl CheckAttrVisitor<'_> {
                 true
             }
             _ => {
-                self.tcx
-                    .sess
-                    .struct_span_err(attr.span, "attribute should be applied to a function")
-                    .span_label(span, "not a function")
-                    .emit();
+                self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
+                    attr_span: attr.span,
+                    defn_span: span,
+                });
                 false
             }
         }
@@ -591,24 +546,17 @@ impl CheckAttrVisitor<'_> {
         match target {
             Target::ForeignStatic | Target::Static => true,
             _ => {
-                self.tcx
-                    .sess
-                    .struct_span_err(attr.span, "attribute should be applied to a static")
-                    .span_label(span, "not a static")
-                    .emit();
+                self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToStatic {
+                    attr_span: attr.span,
+                    defn_span: span,
+                });
                 false
             }
         }
     }
 
     fn doc_attr_str_error(&self, meta: &NestedMetaItem, attr_name: &str) {
-        self.tcx
-            .sess
-            .struct_span_err(
-                meta.span(),
-                &format!("doc {0} attribute expects a string: #[doc({0} = \"a\")]", attr_name),
-            )
-            .emit();
+        self.tcx.sess.emit_err(errors::DocExpectStr { attr_span: meta.span(), attr_name });
     }
 
     fn check_doc_alias_value(
@@ -621,22 +569,12 @@ impl CheckAttrVisitor<'_> {
         aliases: &mut FxHashMap<String, Span>,
     ) -> bool {
         let tcx = self.tcx;
-        let err_fn = move |span: Span, msg: &str| {
-            tcx.sess.span_err(
-                span,
-                &format!(
-                    "`#[doc(alias{})]` {}",
-                    if is_list { "(\"...\")" } else { " = \"...\"" },
-                    msg,
-                ),
-            );
-            false
-        };
+        let span = meta.name_value_literal_span().unwrap_or_else(|| meta.span());
+        let attr_str =
+            &format!("`#[doc(alias{})]`", if is_list { "(\"...\")" } else { " = \"...\"" });
         if doc_alias == kw::Empty {
-            return err_fn(
-                meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
-                "attribute cannot have empty value",
-            );
+            tcx.sess.emit_err(errors::DocAliasEmpty { span, attr_str });
+            return false;
         }
 
         let doc_alias_str = doc_alias.as_str();
@@ -644,23 +582,16 @@ impl CheckAttrVisitor<'_> {
             .chars()
             .find(|&c| c == '"' || c == '\'' || (c.is_whitespace() && c != ' '))
         {
-            self.tcx.sess.span_err(
-                meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
-                &format!(
-                    "{:?} character isn't allowed in `#[doc(alias{})]`",
-                    c,
-                    if is_list { "(\"...\")" } else { " = \"...\"" },
-                ),
-            );
+            tcx.sess.emit_err(errors::DocAliasBadChar { span, attr_str, char_: c });
             return false;
         }
         if doc_alias_str.starts_with(' ') || doc_alias_str.ends_with(' ') {
-            return err_fn(
-                meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
-                "cannot start or end with ' '",
-            );
+            tcx.sess.emit_err(errors::DocAliasStartEnd { span, attr_str });
+            return false;
         }
-        if let Some(err) = match target {
+
+        let span = meta.span();
+        if let Some(location) = match target {
             Target::Impl => Some("implementation block"),
             Target::ForeignMod => Some("extern block"),
             Target::AssocTy => {
@@ -686,19 +617,21 @@ impl CheckAttrVisitor<'_> {
             Target::Param => return false,
             _ => None,
         } {
-            return err_fn(meta.span(), &format!("isn't allowed on {}", err));
+            tcx.sess.emit_err(errors::DocAliasBadLocation { span, attr_str, location });
+            return false;
         }
         let item_name = self.tcx.hir().name(hir_id);
         if item_name == doc_alias {
-            return err_fn(meta.span(), "is the same as the item's name");
+            tcx.sess.emit_err(errors::DocAliasNotAnAlias { span, attr_str });
+            return false;
         }
-        let span = meta.span();
         if let Err(entry) = aliases.try_insert(doc_alias_str.to_owned(), span) {
-            self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, span, |lint| {
-                lint.build("doc alias is duplicated")
-                    .span_label(*entry.entry.get(), "first defined here")
-                    .emit();
-            });
+            self.tcx.emit_spanned_lint(
+                UNUSED_ATTRIBUTES,
+                hir_id,
+                span,
+                errors::DocAliasDuplicated { first_defn: *entry.entry.get() },
+            );
         }
         true
     }
@@ -723,22 +656,12 @@ impl CheckAttrVisitor<'_> {
                         _ => {
                             self.tcx
                                 .sess
-                                .struct_span_err(
-                                    v.span(),
-                                    "`#[doc(alias(\"a\"))]` expects string literals",
-                                )
-                                .emit();
+                                .emit_err(errors::DocAliasNotStringLiteral { span: v.span() });
                             errors += 1;
                         }
                     },
                     None => {
-                        self.tcx
-                            .sess
-                            .struct_span_err(
-                                v.span(),
-                                "`#[doc(alias(\"a\"))]` expects string literals",
-                            )
-                            .emit();
+                        self.tcx.sess.emit_err(errors::DocAliasNotStringLiteral { span: v.span() });
                         errors += 1;
                     }
                 }
@@ -747,14 +670,7 @@ impl CheckAttrVisitor<'_> {
         } else if let Some(doc_alias) = meta.value_str() {
             self.check_doc_alias_value(meta, doc_alias, hir_id, target, false, aliases)
         } else {
-            self.tcx
-                .sess
-                .struct_span_err(
-                    meta.span(),
-                    "doc alias attribute expects a string `#[doc(alias = \"a\")]` or a list of \
-                     strings `#[doc(alias(\"a\", \"b\"))]`",
-                )
-                .emit();
+            self.tcx.sess.emit_err(errors::DocAliasMalformed { span: meta.span() });
             false
         }
     }
@@ -771,35 +687,20 @@ impl CheckAttrVisitor<'_> {
         }) {
             Some(ItemKind::Mod(ref module)) => {
                 if !module.item_ids.is_empty() {
-                    self.tcx
-                        .sess
-                        .struct_span_err(
-                            meta.span(),
-                            "`#[doc(keyword = \"...\")]` can only be used on empty modules",
-                        )
-                        .emit();
+                    self.tcx.sess.emit_err(errors::DocKeywordEmptyMod { span: meta.span() });
                     return false;
                 }
             }
             _ => {
-                self.tcx
-                    .sess
-                    .struct_span_err(
-                        meta.span(),
-                        "`#[doc(keyword = \"...\")]` can only be used on modules",
-                    )
-                    .emit();
+                self.tcx.sess.emit_err(errors::DocKeywordNotMod { span: meta.span() });
                 return false;
             }
         }
         if !rustc_lexer::is_ident(doc_keyword.as_str()) {
-            self.tcx
-                .sess
-                .struct_span_err(
-                    meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
-                    &format!("`{doc_keyword}` is not a valid identifier"),
-                )
-                .emit();
+            self.tcx.sess.emit_err(errors::DocKeywordInvalidIdent {
+                span: meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
+                doc_keyword,
+            });
             return false;
         }
         true
@@ -812,24 +713,12 @@ impl CheckAttrVisitor<'_> {
         }) {
             Some(ItemKind::Impl(ref i)) => {
                 if !matches!(&i.self_ty.kind, hir::TyKind::Tup([_])) {
-                    self.tcx
-                        .sess
-                        .struct_span_err(
-                            meta.span(),
-                            "`#[doc(tuple_variadic)]` must be used on the first of a set of tuple trait impls with varying arity",
-                        )
-                        .emit();
+                    self.tcx.sess.emit_err(errors::DocTupleVariadicNotFirst { span: meta.span() });
                     return false;
                 }
             }
             _ => {
-                self.tcx
-                    .sess
-                    .struct_span_err(
-                        meta.span(),
-                        "`#[doc(keyword = \"...\")]` can only be used on impl blocks",
-                    )
-                    .emit();
+                self.tcx.sess.emit_err(errors::DocKeywordOnlyImpl { span: meta.span() });
                 return false;
             }
         }
@@ -858,13 +747,9 @@ impl CheckAttrVisitor<'_> {
             if let Some((prev_inline, prev_span)) = *specified_inline {
                 if do_inline != prev_inline {
                     let mut spans = MultiSpan::from_spans(vec![prev_span, meta.span()]);
-                    spans.push_span_label(prev_span, "this attribute...");
-                    spans.push_span_label(meta.span(), "...conflicts with this attribute");
-                    self.tcx
-                        .sess
-                        .struct_span_err(spans, "conflicting doc inlining attributes")
-                        .help("remove one of the conflicting attributes")
-                        .emit();
+                    spans.push_span_label(prev_span, fluent::passes::doc_inline_conflict_first);
+                    spans.push_span_label(meta.span(), fluent::passes::doc_inline_conflict_second);
+                    self.tcx.sess.emit_err(errors::DocKeywordConflict { spans });
                     return false;
                 }
                 true
@@ -873,23 +758,14 @@ impl CheckAttrVisitor<'_> {
                 true
             }
         } else {
-            self.tcx.struct_span_lint_hir(
+            self.tcx.emit_spanned_lint(
                 INVALID_DOC_ATTRIBUTES,
                 hir_id,
                 meta.span(),
-                |lint| {
-                    let mut err = lint.build(
-                        "this attribute can only be applied to a `use` item",
-                    );
-                    err.span_label(meta.span(), "only applicable on `use` items");
-                    if attr.style == AttrStyle::Outer {
-                        err.span_label(
-                            self.tcx.hir().span(hir_id),
-                            "not a `use` item",
-                        );
-                    }
-                    err.note("read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#inline-and-no_inline for more information")
-                        .emit();
+                errors::DocInlineOnlyUse {
+                    attr_span: meta.span(),
+                    item_span: (attr.style == AttrStyle::Outer)
+                        .then(|| self.tcx.hir().span(hir_id)),
                 },
             );
             false
@@ -904,15 +780,7 @@ impl CheckAttrVisitor<'_> {
         attr_name: &str,
     ) -> bool {
         if CRATE_HIR_ID == hir_id {
-            self.tcx
-                .sess
-                .struct_span_err(
-                    meta.span(),
-                    &format!(
-                        "`#![doc({attr_name} = \"...\")]` isn't allowed as a crate-level attribute",
-                    ),
-                )
-                .emit();
+            self.tcx.sess.emit_err(errors::DocAttrNotCrateLevel { span: meta.span(), attr_name });
             return false;
         }
         true
@@ -926,36 +794,25 @@ impl CheckAttrVisitor<'_> {
         hir_id: HirId,
     ) -> bool {
         if hir_id != CRATE_HIR_ID {
-            self.tcx.struct_span_lint_hir(
-                INVALID_DOC_ATTRIBUTES,
-                hir_id,
-                meta.span(),
-                |lint| {
-                    let mut err = lint.build(
-                        "this attribute can only be applied at the crate level",
-                    );
-                    if attr.style == AttrStyle::Outer && self.tcx.hir().get_parent_item(hir_id) == CRATE_DEF_ID {
-                        if let Ok(mut src) =
-                            self.tcx.sess.source_map().span_to_snippet(attr.span)
-                        {
-                            src.insert(1, '!');
-                            err.span_suggestion_verbose(
-                                attr.span,
-                                "to apply to the crate, use an inner attribute",
-                                src,
-                                Applicability::MaybeIncorrect,
-                            );
-                        } else {
-                            err.span_help(
-                                attr.span,
-                                "to apply to the crate, use an inner attribute",
-                            );
-                        }
+            self.tcx.struct_span_lint_hir(INVALID_DOC_ATTRIBUTES, hir_id, meta.span(), |lint| {
+                let mut err = lint.build(fluent::passes::attr_crate_level);
+                if attr.style == AttrStyle::Outer
+                    && self.tcx.hir().get_parent_item(hir_id) == CRATE_DEF_ID
+                {
+                    if let Ok(mut src) = self.tcx.sess.source_map().span_to_snippet(attr.span) {
+                        src.insert(1, '!');
+                        err.span_suggestion_verbose(
+                            attr.span,
+                            fluent::passes::suggestion,
+                            src,
+                            Applicability::MaybeIncorrect,
+                        );
+                    } else {
+                        err.span_help(attr.span, fluent::passes::help);
                     }
-                    err.note("read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level for more information")
-                        .emit();
-                },
-            );
+                }
+                err.note(fluent::passes::note).emit();
+            });
             return false;
         }
         true
@@ -970,18 +827,14 @@ impl CheckAttrVisitor<'_> {
                 match i_meta.name_or_empty() {
                     sym::attr | sym::no_crate_inject => {}
                     _ => {
-                        self.tcx.struct_span_lint_hir(
+                        self.tcx.emit_spanned_lint(
                             INVALID_DOC_ATTRIBUTES,
                             hir_id,
                             i_meta.span(),
-                            |lint| {
-                                lint.build(&format!(
-                                    "unknown `doc(test)` attribute `{}`",
-                                    rustc_ast_pretty::pprust::path_to_string(
-                                        &i_meta.meta_item().unwrap().path
-                                    ),
-                                ))
-                                .emit();
+                            errors::DocTestUnknown {
+                                path: rustc_ast_pretty::pprust::path_to_string(
+                                    &i_meta.meta_item().unwrap().path,
+                                ),
                             },
                         );
                         is_valid = false;
@@ -989,9 +842,12 @@ impl CheckAttrVisitor<'_> {
                 }
             }
         } else {
-            self.tcx.struct_span_lint_hir(INVALID_DOC_ATTRIBUTES, hir_id, meta.span(), |lint| {
-                lint.build("`#[doc(test(...)]` takes a list of attributes").emit();
-            });
+            self.tcx.emit_spanned_lint(
+                INVALID_DOC_ATTRIBUTES,
+                hir_id,
+                meta.span(),
+                errors::DocTestTakesList,
+            );
             is_valid = false;
         }
         is_valid
@@ -1093,79 +949,66 @@ impl CheckAttrVisitor<'_> {
 
                         sym::primitive => {
                             if !self.tcx.features().rustdoc_internals {
-                                self.tcx.struct_span_lint_hir(
+                                self.tcx.emit_spanned_lint(
                                     INVALID_DOC_ATTRIBUTES,
                                     hir_id,
                                     i_meta.span,
-                                    |lint| {
-                                        let mut diag = lint.build(
-                                            "`doc(primitive)` should never have been stable",
-                                        );
-                                        diag.emit();
-                                    },
+                                    errors::DocPrimitive,
                                 );
                             }
                         }
 
                         _ => {
-                            self.tcx.struct_span_lint_hir(
-                                INVALID_DOC_ATTRIBUTES,
-                                hir_id,
-                                i_meta.span,
-                                |lint| {
-                                    let mut diag = lint.build(&format!(
-                                        "unknown `doc` attribute `{}`",
-                                        rustc_ast_pretty::pprust::path_to_string(&i_meta.path),
-                                    ));
-                                    if i_meta.has_name(sym::spotlight) {
-                                        diag.note(
-                                            "`doc(spotlight)` was renamed to `doc(notable_trait)`",
-                                        );
-                                        diag.span_suggestion_short(
-                                            i_meta.span,
-                                            "use `notable_trait` instead",
-                                            "notable_trait",
-                                            Applicability::MachineApplicable,
-                                        );
-                                        diag.note("`doc(spotlight)` is now a no-op");
+                            let path = rustc_ast_pretty::pprust::path_to_string(&i_meta.path);
+                            if i_meta.has_name(sym::spotlight) {
+                                self.tcx.emit_spanned_lint(
+                                    INVALID_DOC_ATTRIBUTES,
+                                    hir_id,
+                                    i_meta.span,
+                                    errors::DocTestUnknownSpotlight {
+                                        path,
+                                        span: i_meta.span
                                     }
-                                    if i_meta.has_name(sym::include) {
-                                        if let Some(value) = i_meta.value_str() {
-                                            // if there are multiple attributes, the suggestion would suggest deleting all of them, which is incorrect
-                                            let applicability = if list.len() == 1 {
-                                                Applicability::MachineApplicable
-                                            } else {
-                                                Applicability::MaybeIncorrect
-                                            };
-                                            let inner = if attr.style == AttrStyle::Inner {
-                                                "!"
-                                            } else {
-                                                ""
-                                            };
-                                            diag.span_suggestion(
-                                                attr.meta().unwrap().span,
-                                                "use `doc = include_str!` instead",
-                                                format!(
-                                                    "#{inner}[doc = include_str!(\"{value}\")]",
-                                                ),
-                                                applicability,
-                                            );
-                                        }
+                                );
+                            } else if i_meta.has_name(sym::include) &&
+                                    let Some(value) = i_meta.value_str() {
+                                let applicability = if list.len() == 1 {
+                                    Applicability::MachineApplicable
+                                } else {
+                                    Applicability::MaybeIncorrect
+                                };
+                                // If there are multiple attributes, the suggestion would suggest
+                                // deleting all of them, which is incorrect.
+                                self.tcx.emit_spanned_lint(
+                                    INVALID_DOC_ATTRIBUTES,
+                                    hir_id,
+                                    i_meta.span,
+                                    errors::DocTestUnknownInclude {
+                                        path,
+                                        value: value.to_string(),
+                                        inner: (attr.style == AttrStyle::Inner)
+                                            .then_some("!")
+                                            .unwrap_or(""),
+                                        sugg: (attr.meta().unwrap().span, applicability),
                                     }
-                                    diag.emit();
-                                },
-                            );
+                                );
+                            } else {
+                                self.tcx.emit_spanned_lint(
+                                    INVALID_DOC_ATTRIBUTES,
+                                    hir_id,
+                                    i_meta.span,
+                                    errors::DocTestUnknownAny { path }
+                                );
+                            }
                             is_valid = false;
                         }
                     }
                 } else {
-                    self.tcx.struct_span_lint_hir(
+                    self.tcx.emit_spanned_lint(
                         INVALID_DOC_ATTRIBUTES,
                         hir_id,
                         meta.span(),
-                        |lint| {
-                            lint.build("invalid `doc` attribute").emit();
-                        },
+                        errors::DocInvalid,
                     );
                     is_valid = false;
                 }
@@ -1180,14 +1023,7 @@ impl CheckAttrVisitor<'_> {
         match target {
             Target::Struct | Target::Enum | Target::TyAlias => true,
             _ => {
-                self.tcx
-                    .sess
-                    .struct_span_err(
-                        attr.span,
-                        "`pass_by_value` attribute should be applied to a struct, enum or type alias.",
-                    )
-                    .span_label(span, "is not a struct, enum or type alias")
-                    .emit();
+                self.tcx.sess.emit_err(errors::PassByValue { attr_span: attr.span, span });
                 false
             }
         }
@@ -1197,14 +1033,7 @@ impl CheckAttrVisitor<'_> {
         match target {
             Target::Method(MethodKind::Inherent) => true,
             _ => {
-                self.tcx
-                    .sess
-                    .struct_span_err(
-                        attr.span,
-                        "`rustc_allow_incoherent_impl` attribute should be applied to impl items.",
-                    )
-                    .span_label(span, "the only currently supported targets are inherent methods")
-                    .emit();
+                self.tcx.sess.emit_err(errors::AllowIncoherentImpl { attr_span: attr.span, span });
                 false
             }
         }
@@ -1223,12 +1052,7 @@ impl CheckAttrVisitor<'_> {
             _ => {
                 self.tcx
                     .sess
-                    .struct_span_err(
-                        attr.span,
-                        "`rustc_has_incoherent_inherent_impls` attribute should be applied to types or traits.",
-                    )
-                    .span_label(span, "only adts, extern types and traits are supported")
-                    .emit();
+                    .emit_err(errors::HasIncoherentInherentImpl { attr_span: attr.span, span });
                 false
             }
         }
@@ -1238,19 +1062,12 @@ impl CheckAttrVisitor<'_> {
     fn check_must_use(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool {
         let node = self.tcx.hir().get(hir_id);
         if let Some(kind) = node.fn_kind() && let rustc_hir::IsAsync::Async = kind.asyncness() {
-            self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-                lint.build(
-                    "`must_use` attribute on `async` functions \
-                    applies to the anonymous `Future` returned by the \
-                    function, not the value within",
-                )
-                .span_label(
-                    span,
-                    "this attribute does nothing, the `Future`s \
-                    returned by async functions are already `must_use`",
-                )
-                .emit();
-            });
+            self.tcx.emit_spanned_lint(
+                UNUSED_ATTRIBUTES,
+                hir_id,
+                attr.span,
+                errors::MustUseAsync { span }
+            );
         }
 
         if !matches!(
@@ -1278,12 +1095,12 @@ impl CheckAttrVisitor<'_> {
                 _ => "a",
             };
 
-            self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-                lint.build(&format!(
-                    "`#[must_use]` has no effect when applied to {article} {target}"
-                ))
-                .emit();
-            });
+            self.tcx.emit_spanned_lint(
+                UNUSED_ATTRIBUTES,
+                hir_id,
+                attr.span,
+                errors::MustUseNoEffect { article, target },
+            );
         }
 
         // For now, its always valid
@@ -1295,11 +1112,7 @@ impl CheckAttrVisitor<'_> {
         match target {
             Target::Struct | Target::Enum | Target::Union | Target::Trait => true,
             _ => {
-                self.tcx
-                    .sess
-                    .struct_span_err(attr.span, "`must_not_suspend` attribute should be applied to a struct, enum, or trait")
-                        .span_label(span, "is not a struct, enum, or trait")
-                        .emit();
+                self.tcx.sess.emit_err(errors::MustNotSuspend { attr_span: attr.span, span });
                 false
             }
         }
@@ -1319,16 +1132,12 @@ impl CheckAttrVisitor<'_> {
             _ => {
                 // FIXME: #[cold] was previously allowed on non-functions and some crates used
                 // this, so only emit a warning.
-                self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-                    lint.build("attribute should be applied to a function")
-                        .warn(
-                            "this was previously accepted by the compiler but is \
-                             being phased out; it will become a hard error in \
-                             a future release!",
-                        )
-                        .span_label(span, "not a function")
-                        .emit();
-                });
+                self.tcx.emit_spanned_lint(
+                    UNUSED_ATTRIBUTES,
+                    hir_id,
+                    attr.span,
+                    errors::Cold { span },
+                );
             }
         }
     }
@@ -1343,19 +1152,12 @@ impl CheckAttrVisitor<'_> {
             return;
         }
 
-        self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
-            let mut diag =
-                lint.build("attribute should be applied to an `extern` block with non-Rust ABI");
-            diag.warn(
-                "this was previously accepted by the compiler but is \
-                 being phased out; it will become a hard error in \
-                 a future release!",
-            );
-            if target != Target::ForeignMod {
-                diag.span_label(span, "not an `extern` block");
-            }
-            diag.emit();
-        });
+        self.tcx.emit_spanned_lint(
+            UNUSED_ATTRIBUTES,
+            hir_id,
+            attr.span,
+            errors::Link { span: (target != Target::ForeignMod).then_some(span) },
+        );
     }
 
     /// Checks if `#[link_name]` is applied to an item other than a foreign function or static.
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
new file mode 100644
index 0000000000000..f8e8720ab5474
--- /dev/null
+++ b/compiler/rustc_passes/src/errors.rs
@@ -0,0 +1,362 @@
+use rustc_errors::{Applicability, MultiSpan};
+use rustc_macros::{LintDiagnostic, SessionDiagnostic};
+use rustc_span::{Span, Symbol};
+
+#[derive(LintDiagnostic)]
+#[lint(passes::outer_crate_level_attr)]
+pub struct OuterCrateLevelAttr;
+
+#[derive(LintDiagnostic)]
+#[lint(passes::inner_crate_level_attr)]
+pub struct InnerCrateLevelAttr;
+
+#[derive(LintDiagnostic)]
+#[lint(passes::ignored_attr_with_macro)]
+pub struct IgnoredAttrWithMacro<'a> {
+    pub sym: &'a str,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::ignored_attr)]
+pub struct IgnoredAttr<'a> {
+    pub sym: &'a str,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::inline_ignored_function_prototype)]
+pub struct IgnoredInlineAttrFnProto;
+
+#[derive(LintDiagnostic)]
+#[lint(passes::inline_ignored_constants)]
+#[warn_]
+#[note]
+pub struct IgnoredInlineAttrConstants;
+
+#[derive(SessionDiagnostic)]
+#[error(passes::inline_not_fn_or_closure, code = "E0518")]
+pub struct InlineNotFnOrClosure {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub defn_span: Span,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::no_coverage_ignored_function_prototype)]
+pub struct IgnoredNoCoverageFnProto;
+
+#[derive(LintDiagnostic)]
+#[lint(passes::no_coverage_propagate)]
+pub struct IgnoredNoCoveragePropagate;
+
+#[derive(LintDiagnostic)]
+#[lint(passes::no_coverage_fn_defn)]
+pub struct IgnoredNoCoverageFnDefn;
+
+#[derive(SessionDiagnostic)]
+#[error(passes::no_coverage_not_coverable, code = "E0788")]
+pub struct IgnoredNoCoverageNotCoverable {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub defn_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::should_be_applied_to_fn)]
+pub struct AttrShouldBeAppliedToFn {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub defn_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::naked_tracked_caller, code = "E0736")]
+pub struct NakedTrackedCaller {
+    #[primary_span]
+    pub attr_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::should_be_applied_to_fn, code = "E0739")]
+pub struct TrackedCallerWrongLocation {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub defn_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::should_be_applied_to_struct_enum, code = "E0701")]
+pub struct NonExhaustiveWrongLocation {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub defn_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::should_be_applied_to_trait)]
+pub struct AttrShouldBeAppliedToTrait {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub defn_span: Span,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::target_feature_on_statement)]
+pub struct TargetFeatureOnStatement;
+
+#[derive(SessionDiagnostic)]
+#[error(passes::should_be_applied_to_static)]
+pub struct AttrShouldBeAppliedToStatic {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub defn_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_expect_str)]
+pub struct DocExpectStr<'a> {
+    #[primary_span]
+    pub attr_span: Span,
+    pub attr_name: &'a str,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_alias_empty)]
+pub struct DocAliasEmpty<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub attr_str: &'a str,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_alias_bad_char)]
+pub struct DocAliasBadChar<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub attr_str: &'a str,
+    pub char_: char,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_alias_start_end)]
+pub struct DocAliasStartEnd<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub attr_str: &'a str,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_alias_bad_location)]
+pub struct DocAliasBadLocation<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub attr_str: &'a str,
+    pub location: &'a str,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_alias_not_an_alias)]
+pub struct DocAliasNotAnAlias<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub attr_str: &'a str,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::doc_alias_duplicated)]
+pub struct DocAliasDuplicated {
+    #[label]
+    pub first_defn: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_alias_not_string_literal)]
+pub struct DocAliasNotStringLiteral {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_alias_malformed)]
+pub struct DocAliasMalformed {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_keyword_empty_mod)]
+pub struct DocKeywordEmptyMod {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_keyword_not_mod)]
+pub struct DocKeywordNotMod {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_keyword_invalid_ident)]
+pub struct DocKeywordInvalidIdent {
+    #[primary_span]
+    pub span: Span,
+    pub doc_keyword: Symbol,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_tuple_variadic_not_first)]
+pub struct DocTupleVariadicNotFirst {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_keyword_only_impl)]
+pub struct DocKeywordOnlyImpl {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_inline_conflict)]
+#[help]
+pub struct DocKeywordConflict {
+    #[primary_span]
+    pub spans: MultiSpan,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::doc_inline_only_use)]
+#[note]
+pub struct DocInlineOnlyUse {
+    #[label]
+    pub attr_span: Span,
+    #[label(passes::not_a_use_item_label)]
+    pub item_span: Option<Span>,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::doc_attr_not_crate_level)]
+pub struct DocAttrNotCrateLevel<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub attr_name: &'a str,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::doc_test_unknown)]
+pub struct DocTestUnknown {
+    pub path: String,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::doc_test_takes_list)]
+pub struct DocTestTakesList;
+
+#[derive(LintDiagnostic)]
+#[lint(passes::doc_primitive)]
+pub struct DocPrimitive;
+
+#[derive(LintDiagnostic)]
+#[lint(passes::doc_test_unknown_any)]
+pub struct DocTestUnknownAny {
+    pub path: String,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::doc_test_unknown_spotlight)]
+#[note]
+#[note(passes::no_op_note)]
+pub struct DocTestUnknownSpotlight {
+    pub path: String,
+    #[suggestion_short(applicability = "machine-applicable", code = "notable_trait")]
+    pub span: Span,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::doc_test_unknown_include)]
+pub struct DocTestUnknownInclude {
+    pub path: String,
+    pub value: String,
+    pub inner: &'static str,
+    #[suggestion(code = "#{inner}[doc = include_str!(\"{value}\")]")]
+    pub sugg: (Span, Applicability),
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::doc_invalid)]
+pub struct DocInvalid;
+
+#[derive(SessionDiagnostic)]
+#[error(passes::pass_by_value)]
+pub struct PassByValue {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::allow_incoherent_impl)]
+pub struct AllowIncoherentImpl {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::has_incoherent_inherent_impl)]
+pub struct HasIncoherentInherentImpl {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub span: Span,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::must_use_async)]
+pub struct MustUseAsync {
+    #[label]
+    pub span: Span,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::must_use_no_effect)]
+pub struct MustUseNoEffect {
+    pub article: &'static str,
+    pub target: rustc_hir::Target,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(passes::must_not_suspend)]
+pub struct MustNotSuspend {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub span: Span,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::cold)]
+#[warn_]
+pub struct Cold {
+    #[label]
+    pub span: Span,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(passes::link)]
+#[warn_]
+pub struct Link {
+    #[label]
+    pub span: Option<Span>,
+}
diff --git a/compiler/rustc_passes/src/lib.rs b/compiler/rustc_passes/src/lib.rs
index 497c0931c2182..7b2f83958af85 100644
--- a/compiler/rustc_passes/src/lib.rs
+++ b/compiler/rustc_passes/src/lib.rs
@@ -7,8 +7,8 @@
 #![allow(rustc::potential_query_instability)]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(iter_intersperse)]
-#![feature(let_else)]
 #![feature(let_chains)]
+#![feature(let_else)]
 #![feature(map_try_insert)]
 #![feature(min_specialization)]
 #![feature(try_blocks)]
@@ -27,6 +27,7 @@ pub mod dead;
 mod debugger_visualizer;
 mod diagnostic_items;
 pub mod entry;
+mod errors;
 pub mod hir_id_validator;
 pub mod hir_stats;
 mod lang_items;
diff --git a/compiler/rustc_privacy/src/errors.rs b/compiler/rustc_privacy/src/errors.rs
index 482721d373ab7..b0fac91f6ebc3 100644
--- a/compiler/rustc_privacy/src/errors.rs
+++ b/compiler/rustc_privacy/src/errors.rs
@@ -1,4 +1,4 @@
-use rustc_macros::{SessionDiagnostic, SessionSubdiagnostic};
+use rustc_macros::{LintDiagnostic, SessionDiagnostic, SessionSubdiagnostic};
 use rustc_span::{Span, Symbol};
 
 #[derive(SessionDiagnostic)]
@@ -73,3 +73,19 @@ pub struct InPublicInterface<'a> {
     #[label(privacy::visibility_label)]
     pub vis_span: Span,
 }
+
+#[derive(LintDiagnostic)]
+#[lint(privacy::from_private_dep_in_public_interface)]
+pub struct FromPrivateDependencyInPublicInterface<'a> {
+    pub kind: &'a str,
+    pub descr: String,
+    pub krate: Symbol,
+}
+
+#[derive(LintDiagnostic)]
+#[lint(privacy::private_in_public_lint)]
+pub struct PrivateInPublicLint<'a> {
+    pub vis_descr: &'static str,
+    pub kind: &'a str,
+    pub descr: String,
+}
diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs
index 5b21c04664774..9a835808d4935 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -38,8 +38,8 @@ use std::ops::ControlFlow;
 use std::{cmp, fmt, mem};
 
 use errors::{
-    FieldIsPrivate, FieldIsPrivateLabel, InPublicInterface, InPublicInterfaceTraits, ItemIsPrivate,
-    UnnamedItemIsPrivate,
+    FieldIsPrivate, FieldIsPrivateLabel, FromPrivateDependencyInPublicInterface, InPublicInterface,
+    InPublicInterfaceTraits, ItemIsPrivate, PrivateInPublicLint, UnnamedItemIsPrivate,
 };
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -1716,19 +1716,14 @@ impl SearchInterfaceForPrivateItemsVisitor<'_> {
 
     fn check_def_id(&mut self, def_id: DefId, kind: &str, descr: &dyn fmt::Display) -> bool {
         if self.leaks_private_dep(def_id) {
-            self.tcx.struct_span_lint_hir(
+            self.tcx.emit_spanned_lint(
                 lint::builtin::EXPORTED_PRIVATE_DEPENDENCIES,
                 self.tcx.hir().local_def_id_to_hir_id(self.item_def_id),
                 self.tcx.def_span(self.item_def_id.to_def_id()),
-                |lint| {
-                    lint.build(&format!(
-                        "{} `{}` from private dependency '{}' in public \
-                                                interface",
-                        kind,
-                        descr,
-                        self.tcx.crate_name(def_id.krate)
-                    ))
-                    .emit();
+                FromPrivateDependencyInPublicInterface {
+                    kind,
+                    descr: descr.to_string(),
+                    krate: self.tcx.crate_name(def_id.krate),
                 },
             );
         }
@@ -1754,12 +1749,14 @@ impl SearchInterfaceForPrivateItemsVisitor<'_> {
                 }
             };
             let span = self.tcx.def_span(self.item_def_id.to_def_id());
+            let descr = descr.to_string();
             if self.has_old_errors
                 || self.in_assoc_ty
                 || self.tcx.resolutions(()).has_pub_restricted
             {
                 let descr = descr.to_string();
-                let vis_span = self.tcx.def_span(def_id);
+                let vis_span =
+                    self.tcx.sess.source_map().guess_head_span(self.tcx.def_span(def_id));
                 if kind == "trait" {
                     self.tcx.sess.emit_err(InPublicInterfaceTraits {
                         span,
@@ -1778,19 +1775,11 @@ impl SearchInterfaceForPrivateItemsVisitor<'_> {
                     });
                 }
             } else {
-                let err_code = if kind == "trait" { "E0445" } else { "E0446" };
-                self.tcx.struct_span_lint_hir(
+                self.tcx.emit_spanned_lint(
                     lint::builtin::PRIVATE_IN_PUBLIC,
                     hir_id,
                     span,
-                    |lint| {
-                        lint.build(&format!(
-                            "{} (error {})",
-                            format!("{} {} `{}` in public interface", vis_descr, kind, descr),
-                            err_code
-                        ))
-                        .emit();
-                    },
+                    PrivateInPublicLint { vis_descr, kind, descr },
                 );
             }
         }
diff --git a/compiler/rustc_session/src/code_stats.rs b/compiler/rustc_session/src/code_stats.rs
index cbb03ffd7a083..eede4d16ea378 100644
--- a/compiler/rustc_session/src/code_stats.rs
+++ b/compiler/rustc_session/src/code_stats.rs
@@ -1,11 +1,12 @@
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::Lock;
+use rustc_span::Symbol;
 use rustc_target::abi::{Align, Size};
 use std::cmp::{self, Ordering};
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub struct VariantInfo {
-    pub name: Option<String>,
+    pub name: Option<Symbol>,
     pub kind: SizeKind,
     pub size: u64,
     pub align: u64,
@@ -20,7 +21,7 @@ pub enum SizeKind {
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub struct FieldInfo {
-    pub name: String,
+    pub name: Symbol,
     pub offset: u64,
     pub size: u64,
     pub align: u64,
@@ -119,7 +120,7 @@ impl CodeStats {
                 let VariantInfo { ref name, kind: _, align: _, size, ref fields } = *variant_info;
                 let indent = if !struct_like {
                     let name = match name.as_ref() {
-                        Some(name) => name.to_owned(),
+                        Some(name) => name.to_string(),
                         None => i.to_string(),
                     };
                     println!(
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
index c1af1a0597239..8a679ca005f3d 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
@@ -23,7 +23,7 @@ use rustc_hir::GenericParam;
 use rustc_hir::Item;
 use rustc_hir::Node;
 use rustc_infer::infer::error_reporting::same_type_modulo_infer;
-use rustc_infer::traits::{AmbiguousSelection, TraitEngine};
+use rustc_infer::traits::TraitEngine;
 use rustc_middle::traits::select::OverflowError;
 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::error::ExpectedFound;
@@ -1403,7 +1403,7 @@ trait InferCtxtPrivExt<'hir, 'tcx> {
     fn annotate_source_of_ambiguity(
         &self,
         err: &mut Diagnostic,
-        impls: &[AmbiguousSelection],
+        impls: &[DefId],
         predicate: ty::Predicate<'tcx>,
     );
 
@@ -2036,14 +2036,6 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
                 );
                 match selcx.select_from_obligation(&obligation) {
                     Err(SelectionError::Ambiguous(impls)) if impls.len() > 1 => {
-                        if self.is_tainted_by_errors() && subst.is_none() {
-                            // If `subst.is_none()`, then this is probably two param-env
-                            // candidates or impl candidates that are equal modulo lifetimes.
-                            // Therefore, if we've already emitted an error, just skip this
-                            // one, since it's not particularly actionable.
-                            err.cancel();
-                            return;
-                        }
                         self.annotate_source_of_ambiguity(&mut err, &impls, predicate);
                     }
                     _ => {
@@ -2224,35 +2216,24 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
     fn annotate_source_of_ambiguity(
         &self,
         err: &mut Diagnostic,
-        impls: &[AmbiguousSelection],
+        impls: &[DefId],
         predicate: ty::Predicate<'tcx>,
     ) {
         let mut spans = vec![];
         let mut crates = vec![];
         let mut post = vec![];
-        let mut or_where_clause = false;
-        for ambig in impls {
-            match ambig {
-                AmbiguousSelection::Impl(def_id) => match self.tcx.span_of_impl(*def_id) {
-                    Ok(span) => spans.push(span),
-                    Err(name) => {
-                        crates.push(name);
-                        if let Some(header) = to_pretty_impl_header(self.tcx, *def_id) {
-                            post.push(header);
-                        }
+        for def_id in impls {
+            match self.tcx.span_of_impl(*def_id) {
+                Ok(span) => spans.push(span),
+                Err(name) => {
+                    crates.push(name);
+                    if let Some(header) = to_pretty_impl_header(self.tcx, *def_id) {
+                        post.push(header);
                     }
-                },
-                AmbiguousSelection::ParamEnv(span) => {
-                    or_where_clause = true;
-                    spans.push(*span);
                 }
             }
         }
-        let msg = format!(
-            "multiple `impl`s{} satisfying `{}` found",
-            if or_where_clause { " or `where` clauses" } else { "" },
-            predicate
-        );
+        let msg = format!("multiple `impl`s satisfying `{}` found", predicate);
         let mut crate_names: Vec<_> = crates.iter().map(|n| format!("`{}`", n)).collect();
         crate_names.sort();
         crate_names.dedup();
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index 96d83deeeb7ab..6e8581128dd8e 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -6,11 +6,9 @@
 //!
 //! [rustc dev guide]:https://rustc-dev-guide.rust-lang.org/traits/resolution.html#candidate-assembly
 use hir::LangItem;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-use rustc_infer::traits::util::elaborate_predicates_with_span;
-use rustc_infer::traits::{AmbiguousSelection, TraitEngine};
+use rustc_infer::traits::TraitEngine;
 use rustc_infer::traits::{Obligation, SelectionError, TraitObligation};
 use rustc_lint_defs::builtin::DEREF_INTO_DYN_SUPERTRAIT;
 use rustc_middle::ty::print::with_no_trimmed_paths;
@@ -201,48 +199,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     // and report ambiguity.
                     if i > 1 {
                         debug!("multiple matches, ambig");
-
-                        // Collect a list of (probable) spans that point to a param-env candidate
-                        let tcx = self.infcx.tcx;
-                        let owner = stack.obligation.cause.body_id.owner.to_def_id();
-                        let predicates = tcx.predicates_of(owner).instantiate_identity(tcx);
-                        let param_env_spans: FxHashMap<_, _> = elaborate_predicates_with_span(
-                            tcx,
-                            std::iter::zip(predicates.predicates, predicates.spans),
-                        )
-                        .filter_map(|obligation| {
-                            let kind = obligation.predicate.kind();
-                            if let ty::PredicateKind::Trait(trait_pred) = kind.skip_binder() {
-                                if trait_pred.trait_ref
-                                    == ty::TraitRef::identity(tcx, trait_pred.def_id())
-                                        .skip_binder()
-                                {
-                                    // HACK: Remap the `Self: Trait` predicate that every trait has to a more useful span
-                                    Some((
-                                        kind.rebind(trait_pred),
-                                        tcx.def_span(trait_pred.def_id()),
-                                    ))
-                                } else {
-                                    Some((kind.rebind(trait_pred), obligation.cause.span))
-                                }
-                            } else {
-                                None
-                            }
-                        })
-                        .collect();
-
                         return Err(Ambiguous(
                             candidates
                                 .into_iter()
                                 .filter_map(|c| match c.candidate {
-                                    SelectionCandidate::ImplCandidate(def_id) => {
-                                        Some(AmbiguousSelection::Impl(def_id))
-                                    }
-                                    SelectionCandidate::ParamCandidate(predicate) => {
-                                        Some(AmbiguousSelection::ParamEnv(
-                                            *param_env_spans.get(&predicate)?,
-                                        ))
-                                    }
+                                    SelectionCandidate::ImplCandidate(def_id) => Some(def_id),
                                     _ => None,
                                 })
                                 .collect(),
diff --git a/compiler/rustc_typeck/src/astconv/mod.rs b/compiler/rustc_typeck/src/astconv/mod.rs
index c3205aeb07477..9e4da0580522b 100644
--- a/compiler/rustc_typeck/src/astconv/mod.rs
+++ b/compiler/rustc_typeck/src/astconv/mod.rs
@@ -2486,7 +2486,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                         concrete type's name `{type_name}` instead if you want to \
                                         specify its type parameters"
                                     ),
-                                    type_name.to_string(),
+                                    type_name,
                                     Applicability::MaybeIncorrect,
                                 );
                             }
diff --git a/compiler/rustc_typeck/src/check/compare_method.rs b/compiler/rustc_typeck/src/check/compare_method.rs
index 1f921ca835890..a53217ef81882 100644
--- a/compiler/rustc_typeck/src/check/compare_method.rs
+++ b/compiler/rustc_typeck/src/check/compare_method.rs
@@ -544,7 +544,7 @@ fn compare_self_type<'tcx>(
             if let Some(span) = tcx.hir().span_if_local(trait_m.def_id) {
                 err.span_label(span, format!("trait method declared without `{self_descr}`"));
             } else {
-                err.note_trait_signature(trait_m.name.to_string(), trait_m.signature(tcx));
+                err.note_trait_signature(trait_m.name, trait_m.signature(tcx));
             }
             let reported = err.emit();
             return Err(reported);
@@ -564,7 +564,7 @@ fn compare_self_type<'tcx>(
             if let Some(span) = tcx.hir().span_if_local(trait_m.def_id) {
                 err.span_label(span, format!("`{self_descr}` used in trait"));
             } else {
-                err.note_trait_signature(trait_m.name.to_string(), trait_m.signature(tcx));
+                err.note_trait_signature(trait_m.name, trait_m.signature(tcx));
             }
             let reported = err.emit();
             return Err(reported);
@@ -803,7 +803,7 @@ fn compare_number_of_method_arguments<'tcx>(
                 ),
             );
         } else {
-            err.note_trait_signature(trait_m.name.to_string(), trait_m.signature(tcx));
+            err.note_trait_signature(trait_m.name, trait_m.signature(tcx));
         }
         err.span_label(
             impl_span,
diff --git a/compiler/rustc_typeck/src/check/expr.rs b/compiler/rustc_typeck/src/check/expr.rs
index b52cb8e99d186..02e493f725864 100644
--- a/compiler/rustc_typeck/src/check/expr.rs
+++ b/compiler/rustc_typeck/src/check/expr.rs
@@ -1856,7 +1856,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let remaining_private_fields_len = remaining_private_fields.len();
             let names = match &remaining_private_fields
                 .iter()
-                .map(|(name, _, _)| name.to_string())
+                .map(|(name, _, _)| name)
                 .collect::<Vec<_>>()[..]
             {
                 _ if remaining_private_fields_len > 6 => String::new(),
diff --git a/compiler/rustc_typeck/src/check/method/suggest.rs b/compiler/rustc_typeck/src/check/method/suggest.rs
index 7bf167426f748..7f96e421a9ae3 100644
--- a/compiler/rustc_typeck/src/check/method/suggest.rs
+++ b/compiler/rustc_typeck/src/check/method/suggest.rs
@@ -19,6 +19,7 @@ use rustc_middle::ty::print::with_crate_prefix;
 use rustc_middle::ty::ToPolyTraitRef;
 use rustc_middle::ty::{self, DefIdTree, ToPredicate, Ty, TyCtxt, TypeVisitable};
 use rustc_span::symbol::{kw, sym, Ident};
+use rustc_span::Symbol;
 use rustc_span::{lev_distance, source_map, ExpnKind, FileName, MacroKind, Span};
 use rustc_trait_selection::traits::error_reporting::on_unimplemented::InferCtxtExt as _;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
@@ -1548,7 +1549,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             Option<ObligationCause<'tcx>>,
         )],
     ) {
-        let mut derives = Vec::<(String, Span, String)>::new();
+        let mut derives = Vec::<(String, Span, Symbol)>::new();
         let mut traits = Vec::<Span>::new();
         for (pred, _, _) in unsatisfied_predicates {
             let ty::PredicateKind::Trait(trait_pred) = pred.kind().skip_binder() else { continue };
@@ -1581,12 +1582,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 derives.push((
                                     self_name.clone(),
                                     self_span,
-                                    parent_diagnostic_name.to_string(),
+                                    parent_diagnostic_name,
                                 ));
                             }
                         }
                     }
-                    derives.push((self_name, self_span, diagnostic_name.to_string()));
+                    derives.push((self_name, self_span, diagnostic_name));
                 } else {
                     traits.push(self.tcx.def_span(trait_pred.def_id()));
                 }
@@ -1609,7 +1610,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     continue;
                 }
             }
-            derives_grouped.push((self_name, self_span, trait_name));
+            derives_grouped.push((self_name, self_span, trait_name.to_string()));
         }
 
         let len = traits.len();
diff --git a/compiler/rustc_typeck/src/check/mod.rs b/compiler/rustc_typeck/src/check/mod.rs
index d6160266dd7d9..849e96445d3ea 100644
--- a/compiler/rustc_typeck/src/check/mod.rs
+++ b/compiler/rustc_typeck/src/check/mod.rs
@@ -25,7 +25,7 @@ can be broken down into several distinct phases:
 
 - regionck: after main is complete, the regionck pass goes over all
   types looking for regions and making sure that they did not escape
-  into places they are not in scope.  This may also influence the
+  into places where they are not in scope.  This may also influence the
   final assignments of the various region variables if there is some
   flexibility.
 
diff --git a/compiler/rustc_typeck/src/impl_wf_check.rs b/compiler/rustc_typeck/src/impl_wf_check.rs
index e7ca70de4ba71..8c26c96816d9b 100644
--- a/compiler/rustc_typeck/src/impl_wf_check.rs
+++ b/compiler/rustc_typeck/src/impl_wf_check.rs
@@ -17,7 +17,7 @@ use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, TyCtxt, TypeVisitable};
-use rustc_span::Span;
+use rustc_span::{Span, Symbol};
 
 use std::collections::hash_map::Entry::{Occupied, Vacant};
 
@@ -123,12 +123,7 @@ fn enforce_impl_params_are_constrained(tcx: TyCtxt<'_>, impl_def_id: LocalDefId)
             ty::GenericParamDefKind::Type { .. } => {
                 let param_ty = ty::ParamTy::for_def(param);
                 if !input_parameters.contains(&cgp::Parameter::from(param_ty)) {
-                    report_unused_parameter(
-                        tcx,
-                        tcx.def_span(param.def_id),
-                        "type",
-                        &param_ty.to_string(),
-                    );
+                    report_unused_parameter(tcx, tcx.def_span(param.def_id), "type", param_ty.name);
                 }
             }
             ty::GenericParamDefKind::Lifetime => {
@@ -140,7 +135,7 @@ fn enforce_impl_params_are_constrained(tcx: TyCtxt<'_>, impl_def_id: LocalDefId)
                         tcx,
                         tcx.def_span(param.def_id),
                         "lifetime",
-                        &param.name.to_string(),
+                        param.name,
                     );
                 }
             }
@@ -151,7 +146,7 @@ fn enforce_impl_params_are_constrained(tcx: TyCtxt<'_>, impl_def_id: LocalDefId)
                         tcx,
                         tcx.def_span(param.def_id),
                         "const",
-                        &param_ct.to_string(),
+                        param_ct.name,
                     );
                 }
             }
@@ -178,7 +173,7 @@ fn enforce_impl_params_are_constrained(tcx: TyCtxt<'_>, impl_def_id: LocalDefId)
     // used elsewhere are not projected back out.
 }
 
-fn report_unused_parameter(tcx: TyCtxt<'_>, span: Span, kind: &str, name: &str) {
+fn report_unused_parameter(tcx: TyCtxt<'_>, span: Span, kind: &str, name: Symbol) {
     let mut err = struct_span_err!(
         tcx.sess,
         span,
diff --git a/library/alloc/src/slice.rs b/library/alloc/src/slice.rs
index 4a9cecd9b4e1a..63d4d94529008 100644
--- a/library/alloc/src/slice.rs
+++ b/library/alloc/src/slice.rs
@@ -836,14 +836,14 @@ impl<T: Clone, V: Borrow<[T]>> Join<&[T]> for [V] {
 ////////////////////////////////////////////////////////////////////////////////
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Borrow<[T]> for Vec<T> {
+impl<T, A: Allocator> Borrow<[T]> for Vec<T, A> {
     fn borrow(&self) -> &[T] {
         &self[..]
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> BorrowMut<[T]> for Vec<T> {
+impl<T, A: Allocator> BorrowMut<[T]> for Vec<T, A> {
     fn borrow_mut(&mut self) -> &mut [T] {
         &mut self[..]
     }
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 2c98cba90d718..d6260b8ca06e4 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -2120,8 +2120,9 @@ fn clean_use_statement<'tcx>(
     // forcefully don't inline if this is not public or if the
     // #[doc(no_inline)] attribute is present.
     // Don't inline doc(hidden) imports so they can be stripped at a later stage.
-    let mut denied = !(visibility.is_public()
-        || (cx.render_options.document_private && is_visible_from_parent_mod))
+    let mut denied = cx.output_format.is_json()
+        || !(visibility.is_public()
+            || (cx.render_options.document_private && is_visible_from_parent_mod))
         || pub_underscore
         || attrs.iter().any(|a| {
             a.has_name(sym::doc)
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index a658e78bf60c6..0e9a9e0e50646 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -81,6 +81,8 @@ pub(crate) struct DocContext<'tcx> {
     pub(crate) inlined: FxHashSet<ItemId>,
     /// Used by `calculate_doc_coverage`.
     pub(crate) output_format: OutputFormat,
+    /// Used by `strip_private`.
+    pub(crate) show_coverage: bool,
 }
 
 impl<'tcx> DocContext<'tcx> {
@@ -381,6 +383,7 @@ pub(crate) fn run_global_ctxt(
         inlined: FxHashSet::default(),
         output_format,
         render_options,
+        show_coverage,
     };
 
     // Small hack to force the Sized trait to be present.
diff --git a/src/librustdoc/json/conversions.rs b/src/librustdoc/json/conversions.rs
index db2ad953f6aa0..2598b9b0b28c2 100644
--- a/src/librustdoc/json/conversions.rs
+++ b/src/librustdoc/json/conversions.rs
@@ -43,7 +43,16 @@ impl JsonRenderer<'_> {
         let span = item.span(self.tcx);
         let clean::Item { name, attrs: _, kind: _, visibility, item_id, cfg: _ } = item;
         let inner = match *item.kind {
-            clean::StrippedItem(_) | clean::KeywordItem(_) => return None,
+            clean::KeywordItem(_) => return None,
+            clean::StrippedItem(ref inner) => {
+                match &**inner {
+                    // We document non-empty stripped modules as with `Module::is_stripped` set to
+                    // `true`, to prevent contained items from being orphaned for downstream users,
+                    // as JSON does no inlining.
+                    clean::ModuleItem(m) if !m.items.is_empty() => from_clean_item(item, self.tcx),
+                    _ => return None,
+                }
+            }
             _ => from_clean_item(item, self.tcx),
         };
         Some(Item {
@@ -220,7 +229,9 @@ fn from_clean_item(item: clean::Item, tcx: TyCtxt<'_>) -> ItemEnum {
     let header = item.fn_header(tcx);
 
     match *item.kind {
-        ModuleItem(m) => ItemEnum::Module(Module { is_crate, items: ids(m.items, tcx) }),
+        ModuleItem(m) => {
+            ItemEnum::Module(Module { is_crate, items: ids(m.items, tcx), is_stripped: false })
+        }
         ImportItem(i) => ItemEnum::Import(i.into_tcx(tcx)),
         StructItem(s) => ItemEnum::Struct(s.into_tcx(tcx)),
         UnionItem(u) => ItemEnum::Union(u.into_tcx(tcx)),
@@ -257,8 +268,19 @@ fn from_clean_item(item: clean::Item, tcx: TyCtxt<'_>) -> ItemEnum {
             bounds: b.into_iter().map(|x| x.into_tcx(tcx)).collect(),
             default: Some(t.item_type.unwrap_or(t.type_).into_tcx(tcx)),
         },
-        // `convert_item` early returns `None` for striped items and keywords.
-        StrippedItem(_) | KeywordItem(_) => unreachable!(),
+        // `convert_item` early returns `None` for stripped items and keywords.
+        KeywordItem(_) => unreachable!(),
+        StrippedItem(inner) => {
+            match *inner {
+                ModuleItem(m) => ItemEnum::Module(Module {
+                    is_crate,
+                    items: ids(m.items, tcx),
+                    is_stripped: true,
+                }),
+                // `convert_item` early returns `None` for stripped items we're not including
+                _ => unreachable!(),
+            }
+        }
         ExternCrateItem { ref src } => ItemEnum::ExternCrate {
             name: name.as_ref().unwrap().to_string(),
             rename: src.map(|x| x.to_string()),
diff --git a/src/librustdoc/json/mod.rs b/src/librustdoc/json/mod.rs
index c7251b5115287..6364d00d0624e 100644
--- a/src/librustdoc/json/mod.rs
+++ b/src/librustdoc/json/mod.rs
@@ -21,6 +21,7 @@ use rustc_span::def_id::LOCAL_CRATE;
 use rustdoc_json_types as types;
 
 use crate::clean::types::{ExternalCrate, ExternalLocation};
+use crate::clean::ItemKind;
 use crate::config::RenderOptions;
 use crate::docfs::PathError;
 use crate::error::Error;
@@ -175,6 +176,14 @@ impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
     /// the hashmap because certain items (traits and types) need to have their mappings for trait
     /// implementations filled out before they're inserted.
     fn item(&mut self, item: clean::Item) -> Result<(), Error> {
+        trace!("rendering {} {:?}", item.type_(), item.name);
+
+        // Flatten items that recursively store other items. We include orphaned items from
+        // stripped modules and etc that are otherwise reachable.
+        if let ItemKind::StrippedItem(inner) = &*item.kind {
+            inner.inner_items().for_each(|i| self.item(i.clone()).unwrap());
+        }
+
         // Flatten items that recursively store other items
         item.kind.inner_items().for_each(|i| self.item(i.clone()).unwrap());
 
diff --git a/src/librustdoc/passes/strip_private.rs b/src/librustdoc/passes/strip_private.rs
index 6c94912bc5368..9ba841a31cf95 100644
--- a/src/librustdoc/passes/strip_private.rs
+++ b/src/librustdoc/passes/strip_private.rs
@@ -24,6 +24,7 @@ pub(crate) fn strip_private(mut krate: clean::Crate, cx: &mut DocContext<'_>) ->
             retained: &mut retained,
             access_levels: &cx.cache.access_levels,
             update_retained: true,
+            is_json_output: cx.output_format.is_json() && !cx.show_coverage,
         };
         krate = ImportStripper.fold_crate(stripper.fold_crate(krate));
     }
diff --git a/src/librustdoc/passes/stripper.rs b/src/librustdoc/passes/stripper.rs
index 0fd124e615415..5f2f50e712b53 100644
--- a/src/librustdoc/passes/stripper.rs
+++ b/src/librustdoc/passes/stripper.rs
@@ -3,7 +3,7 @@ use rustc_hir::def_id::DefId;
 use rustc_middle::middle::privacy::AccessLevels;
 use std::mem;
 
-use crate::clean::{self, Item, ItemIdSet};
+use crate::clean::{self, Item, ItemId, ItemIdSet};
 use crate::fold::{strip_item, DocFolder};
 use crate::formats::cache::Cache;
 
@@ -11,6 +11,21 @@ pub(crate) struct Stripper<'a> {
     pub(crate) retained: &'a mut ItemIdSet,
     pub(crate) access_levels: &'a AccessLevels<DefId>,
     pub(crate) update_retained: bool,
+    pub(crate) is_json_output: bool,
+}
+
+impl<'a> Stripper<'a> {
+    // We need to handle this differently for the JSON output because some non exported items could
+    // be used in public API. And so, we need these items as well. `is_exported` only checks if they
+    // are in the public API, which is not enough.
+    #[inline]
+    fn is_item_reachable(&self, item_id: ItemId) -> bool {
+        if self.is_json_output {
+            self.access_levels.is_reachable(item_id.expect_def_id())
+        } else {
+            self.access_levels.is_exported(item_id.expect_def_id())
+        }
+    }
 }
 
 impl<'a> DocFolder for Stripper<'a> {
@@ -45,9 +60,8 @@ impl<'a> DocFolder for Stripper<'a> {
             | clean::TraitAliasItem(..)
             | clean::MacroItem(..)
             | clean::ForeignTypeItem => {
-                if i.item_id.is_local()
-                    && !self.access_levels.is_exported(i.item_id.expect_def_id())
-                {
+                let item_id = i.item_id;
+                if item_id.is_local() && !self.is_item_reachable(item_id) {
                     debug!("Stripper: stripping {:?} {:?}", i.type_(), i.name);
                     return None;
                 }
diff --git a/src/librustdoc/visit_ast.rs b/src/librustdoc/visit_ast.rs
index ac934f6925d0b..ca7a20bf3688a 100644
--- a/src/librustdoc/visit_ast.rs
+++ b/src/librustdoc/visit_ast.rs
@@ -190,6 +190,10 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
     ) -> bool {
         debug!("maybe_inline_local res: {:?}", res);
 
+        if self.cx.output_format.is_json() {
+            return false;
+        }
+
         let tcx = self.cx.tcx;
         let Some(res_did) = res.opt_def_id() else {
             return false;
diff --git a/src/rustdoc-json-types/lib.rs b/src/rustdoc-json-types/lib.rs
index 1168a89a8b2bf..761e94c7ebbc4 100644
--- a/src/rustdoc-json-types/lib.rs
+++ b/src/rustdoc-json-types/lib.rs
@@ -9,7 +9,7 @@ use std::path::PathBuf;
 use serde::{Deserialize, Serialize};
 
 /// rustdoc format-version.
-pub const FORMAT_VERSION: u32 = 15;
+pub const FORMAT_VERSION: u32 = 16;
 
 /// A `Crate` is the root of the emitted JSON blob. It contains all type/documentation information
 /// about the language items in the local crate, as well as info about external items to allow
@@ -245,6 +245,9 @@ pub enum ItemEnum {
 pub struct Module {
     pub is_crate: bool,
     pub items: Vec<Id>,
+    /// If `true`, this module is not part of the public API, but it contains
+    /// items that are re-exported as public API.
+    pub is_stripped: bool,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
diff --git a/src/test/rustdoc-gui/escape-key.goml b/src/test/rustdoc-gui/escape-key.goml
index d083b0ae0c931..a5afb037d0fd5 100644
--- a/src/test/rustdoc-gui/escape-key.goml
+++ b/src/test/rustdoc-gui/escape-key.goml
@@ -3,6 +3,8 @@
 goto: file://|DOC_PATH|/test_docs/index.html
 // First, we check that the search results are hidden when the Escape key is pressed.
 write: (".search-input", "test")
+// To be SURE that the search will be run.
+press-key: 'Enter'
 wait-for: "#search h1" // The search element is empty before the first search 
 // Check that the currently displayed element is search.
 wait-for: "#alternative-display #search"
diff --git a/src/test/rustdoc-gui/search-filter.goml b/src/test/rustdoc-gui/search-filter.goml
index d0b3175114cce..d645e23706161 100644
--- a/src/test/rustdoc-gui/search-filter.goml
+++ b/src/test/rustdoc-gui/search-filter.goml
@@ -2,6 +2,8 @@
 goto: file://|DOC_PATH|/test_docs/index.html
 show-text: true
 write: (".search-input", "test")
+// To be SURE that the search will be run.
+press-key: 'Enter'
 // Waiting for the search results to appear...
 wait-for: "#titles"
 assert-text: ("#results .externcrate", "test_docs")
diff --git a/src/test/rustdoc-gui/search-reexport.goml b/src/test/rustdoc-gui/search-reexport.goml
index 557781d481092..5ef890d472b90 100644
--- a/src/test/rustdoc-gui/search-reexport.goml
+++ b/src/test/rustdoc-gui/search-reexport.goml
@@ -7,6 +7,8 @@ reload:
 assert-text: ("//*[@id='reexport.TheStdReexport']", "pub use ::std as TheStdReexport;")
 assert-css: ("//*[@id='reexport.TheStdReexport']", {"background-color": "rgba(0, 0, 0, 0)"})
 write: (".search-input", "TheStdReexport")
+// To be SURE that the search will be run.
+press-key: 'Enter'
 wait-for: "//a[@class='result-import']"
 assert-attribute: (
     "//a[@class='result-import']",
@@ -18,6 +20,8 @@ click: "//a[@class='result-import']"
 wait-for-css: ("//*[@id='reexport.TheStdReexport']", {"background-color": "rgb(73, 74, 61)"})
 
 // We now check that the alias is working as well on the reexport.
+// To be SURE that the search will be run.
+press-key: 'Enter'
 write: (".search-input", "AliasForTheStdReexport")
 wait-for: "//a[@class='result-import']"
 assert-text: (
diff --git a/src/test/rustdoc-gui/search-result-color.goml b/src/test/rustdoc-gui/search-result-color.goml
index 901634fe0e635..9a49ae2c6b853 100644
--- a/src/test/rustdoc-gui/search-result-color.goml
+++ b/src/test/rustdoc-gui/search-result-color.goml
@@ -89,6 +89,8 @@ show-text: true
 // We reload the page so the local storage settings are being used.
 reload:
 write: (".search-input", "thisisanalias")
+// To be SURE that the search will be run.
+press-key: 'Enter'
 // Waiting for the search results to appear...
 wait-for: "#titles"
 // Checking that the colors for the alias element are the ones expected.
diff --git a/src/test/rustdoc-gui/search-result-display.goml b/src/test/rustdoc-gui/search-result-display.goml
index b31905a126a0e..6295d7fae8907 100644
--- a/src/test/rustdoc-gui/search-result-display.goml
+++ b/src/test/rustdoc-gui/search-result-display.goml
@@ -2,6 +2,8 @@
 goto: file://|DOC_PATH|/test_docs/index.html
 size: (900, 1000)
 write: (".search-input", "test")
+// To be SURE that the search will be run.
+press-key: 'Enter'
 wait-for: "#search-settings"
 // The width is returned by "getComputedStyle" which returns the exact number instead of the
 // CSS rule which is "50%"...
diff --git a/src/test/rustdoc-gui/search-result-keyword.goml b/src/test/rustdoc-gui/search-result-keyword.goml
index 8b50c5c5e1a5b..16ae10431acf2 100644
--- a/src/test/rustdoc-gui/search-result-keyword.goml
+++ b/src/test/rustdoc-gui/search-result-keyword.goml
@@ -1,6 +1,8 @@
 // Checks that the "keyword" results have the expected text alongside them.
 goto: file://|DOC_PATH|/test_docs/index.html
 write: (".search-input", "CookieMonster")
+// To be SURE that the search will be run.
+press-key: 'Enter'
 // Waiting for the search results to appear...
 wait-for: "#titles"
 // Note: The two next assert commands could be merged as one but readability would be
diff --git a/src/test/rustdoc-gui/search-tab-change-title-fn-sig.goml b/src/test/rustdoc-gui/search-tab-change-title-fn-sig.goml
index 763927f9d0fe9..9d506c1519e6b 100644
--- a/src/test/rustdoc-gui/search-tab-change-title-fn-sig.goml
+++ b/src/test/rustdoc-gui/search-tab-change-title-fn-sig.goml
@@ -2,6 +2,8 @@
 // First, try a search-by-name
 goto: file://|DOC_PATH|/test_docs/index.html
 write: (".search-input", "Foo")
+// To be SURE that the search will be run.
+press-key: 'Enter'
 // Waiting for the search results to appear...
 wait-for: "#titles"
 assert-attribute: ("#titles > button:nth-of-type(1)", {"class": "selected"})
@@ -22,6 +24,8 @@ wait-for-attribute: ("#titles > button:nth-of-type(3)", {"class": "selected"})
 // Now try search-by-return
 goto: file://|DOC_PATH|/test_docs/index.html
 write: (".search-input", "-> String")
+// To be SURE that the search will be run.
+press-key: 'Enter'
 // Waiting for the search results to appear...
 wait-for: "#titles"
 assert-attribute: ("#titles > button:nth-of-type(1)", {"class": "selected"})
@@ -42,6 +46,8 @@ wait-for-attribute: ("#titles > button:nth-of-type(1)", {"class": "selected"})
 // Try with a search-by-return with no results
 goto: file://|DOC_PATH|/test_docs/index.html
 write: (".search-input", "-> Something")
+// To be SURE that the search will be run.
+press-key: 'Enter'
 // Waiting for the search results to appear...
 wait-for: "#titles"
 assert-attribute: ("#titles > button:nth-of-type(1)", {"class": "selected"})
@@ -50,6 +56,8 @@ assert-text: ("#titles > button:nth-of-type(1)", "In Function Return Types", STA
 // Try with a search-by-parameter
 goto: file://|DOC_PATH|/test_docs/index.html
 write: (".search-input", "usize pattern")
+// To be SURE that the search will be run.
+press-key: 'Enter'
 // Waiting for the search results to appear...
 wait-for: "#titles"
 assert-attribute: ("#titles > button:nth-of-type(1)", {"class": "selected"})
@@ -58,6 +66,8 @@ assert-text: ("#titles > button:nth-of-type(1)", "In Function Parameters", START
 // Try with a search-by-parameter-and-return
 goto: file://|DOC_PATH|/test_docs/index.html
 write: (".search-input", "pattern -> str")
+// To be SURE that the search will be run.
+press-key: 'Enter'
 // Waiting for the search results to appear...
 wait-for: "#titles"
 assert-attribute: ("#titles > button:nth-of-type(1)", {"class": "selected"})
diff --git a/src/test/rustdoc-gui/settings.goml b/src/test/rustdoc-gui/settings.goml
index c402c7991c8bb..8a3365d3cc25e 100644
--- a/src/test/rustdoc-gui/settings.goml
+++ b/src/test/rustdoc-gui/settings.goml
@@ -20,6 +20,8 @@ wait-for-css: ("#settings", {"display": "none"})
 // Let's click on it when the search results are displayed.
 focus: ".search-input"
 write: "test"
+// To be SURE that the search will be run.
+press-key: 'Enter'
 wait-for: "#alternative-display #search"
 click: "#settings-menu"
 wait-for-css: ("#settings", {"display": "block"})
diff --git a/src/test/rustdoc-json/doc_hidden_failure.rs b/src/test/rustdoc-json/doc_hidden_failure.rs
new file mode 100644
index 0000000000000..5c4ccf996a54f
--- /dev/null
+++ b/src/test/rustdoc-json/doc_hidden_failure.rs
@@ -0,0 +1,22 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/98007>.
+
+#![feature(no_core)]
+#![no_core]
+
+mod auto {
+    mod action_row {
+        pub struct ActionRowBuilder;
+    }
+
+    #[doc(hidden)]
+    pub mod builders {
+        pub use super::action_row::ActionRowBuilder;
+    }
+}
+
+// @count doc_hidden_failure.json "$.index[*][?(@.name=='builders')]" 2
+pub use auto::*;
+
+pub mod builders {
+    pub use crate::auto::builders::*;
+}
diff --git a/src/test/rustdoc-json/reexport/auxiliary/pub-struct.rs b/src/test/rustdoc-json/reexport/auxiliary/pub-struct.rs
new file mode 100644
index 0000000000000..4a835673a596b
--- /dev/null
+++ b/src/test/rustdoc-json/reexport/auxiliary/pub-struct.rs
@@ -0,0 +1 @@
+pub struct Foo;
diff --git a/src/test/rustdoc-json/reexport/glob_extern.rs b/src/test/rustdoc-json/reexport/glob_extern.rs
index 831c185f6b136..ba1cfd8a0b577 100644
--- a/src/test/rustdoc-json/reexport/glob_extern.rs
+++ b/src/test/rustdoc-json/reexport/glob_extern.rs
@@ -3,15 +3,16 @@
 #![no_core]
 #![feature(no_core)]
 
-// @!has glob_extern.json "$.index[*][?(@.name=='mod1')]"
+// @is glob_extern.json "$.index[*][?(@.name=='mod1')].kind" \"module\"
+// @is glob_extern.json "$.index[*][?(@.name=='mod1')].inner.is_stripped" "true"
 mod mod1 {
     extern "C" {
-        // @set public_fn_id = - "$.index[*][?(@.name=='public_fn')].id"
+        // @has - "$.index[*][?(@.name=='public_fn')].id"
         pub fn public_fn();
         // @!has - "$.index[*][?(@.name=='private_fn')]"
         fn private_fn();
     }
 }
 
-// @has - "$.index[*][?(@.name=='glob_extern')].inner.items[*]" $public_fn_id
+// @is - "$.index[*][?(@.kind=='import')].inner.glob" true
 pub use mod1::*;
diff --git a/src/test/rustdoc-json/reexport/glob_private.rs b/src/test/rustdoc-json/reexport/glob_private.rs
index e907de9236776..e6a44748c25fb 100644
--- a/src/test/rustdoc-json/reexport/glob_private.rs
+++ b/src/test/rustdoc-json/reexport/glob_private.rs
@@ -3,9 +3,11 @@
 #![no_core]
 #![feature(no_core)]
 
-// @!has glob_private.json "$.index[*][?(@.name=='mod1')]"
+// @is glob_private.json "$.index[*][?(@.name=='mod1')].kind" \"module\"
+// @is glob_private.json "$.index[*][?(@.name=='mod1')].inner.is_stripped" "true"
 mod mod1 {
-    // @!has - "$.index[*][?(@.name=='mod2')]"
+    // @is - "$.index[*][?(@.name=='mod2')].kind" \"module\"
+    // @is - "$.index[*][?(@.name=='mod2')].inner.is_stripped" "true"
     mod mod2 {
         // @set m2pub_id = - "$.index[*][?(@.name=='Mod2Public')].id"
         pub struct Mod2Public;
@@ -13,15 +15,18 @@ mod mod1 {
         // @!has - "$.index[*][?(@.name=='Mod2Private')]"
         struct Mod2Private;
     }
+
+    // @has - "$.index[*][?(@.kind=='import' && @.inner.name=='mod2')]"
     pub use self::mod2::*;
 
     // @set m1pub_id = - "$.index[*][?(@.name=='Mod1Public')].id"
     pub struct Mod1Public;
-
     // @!has - "$.index[*][?(@.name=='Mod1Private')]"
     struct Mod1Private;
 }
+
+// @has - "$.index[*][?(@.kind=='import' && @.inner.name=='mod1')]"
 pub use mod1::*;
 
-// @has - "$.index[*][?(@.name=='glob_private')].inner.items[*]" $m2pub_id
-// @has - "$.index[*][?(@.name=='glob_private')].inner.items[*]" $m1pub_id
+// @has - "$.index[*][?(@.name=='mod2')].inner.items[*]" $m2pub_id
+// @has - "$.index[*][?(@.name=='mod1')].inner.items[*]" $m1pub_id
diff --git a/src/test/rustdoc-json/reexport/in_root_and_mod.rs b/src/test/rustdoc-json/reexport/in_root_and_mod.rs
index e3cecbdd7ff2f..7bf10a9868616 100644
--- a/src/test/rustdoc-json/reexport/in_root_and_mod.rs
+++ b/src/test/rustdoc-json/reexport/in_root_and_mod.rs
@@ -1,15 +1,17 @@
 #![feature(no_core)]
 #![no_core]
 
+// @is in_root_and_mod.json "$.index[*][?(@.name=='foo')].kind" \"module\"
+// @is in_root_and_mod.json "$.index[*][?(@.name=='foo')].inner.is_stripped" "true"
 mod foo {
-    // @set foo_id = in_root_and_mod.json "$.index[*][?(@.name=='Foo')].id"
+    // @has - "$.index[*][?(@.name=='Foo')]"
     pub struct Foo;
 }
 
-// @has - "$.index[*][?(@.name=='in_root_and_mod')].inner.items[*]" $foo_id
+// @has - "$.index[*][?(@.kind=='import' && @.inner.source=='foo::Foo')]"
 pub use foo::Foo;
 
 pub mod bar {
-    // @has - "$.index[*][?(@.name=='bar')].inner.items[*]" $foo_id
+    // @has - "$.index[*][?(@.kind=='import' && @.inner.source=='crate::foo::Foo')]"
     pub use crate::foo::Foo;
 }
diff --git a/src/test/rustdoc-json/reexport/private_twice_one_inline.rs b/src/test/rustdoc-json/reexport/private_twice_one_inline.rs
new file mode 100644
index 0000000000000..327b0f45fdd54
--- /dev/null
+++ b/src/test/rustdoc-json/reexport/private_twice_one_inline.rs
@@ -0,0 +1,18 @@
+// aux-build:pub-struct.rs
+
+// Test for the ICE in rust/83057
+// Am external type re-exported with different attributes shouldn't cause an error
+
+#![no_core]
+#![feature(no_core)]
+
+extern crate pub_struct as foo;
+
+#[doc(inline)]
+pub use foo::Foo;
+
+pub mod bar {
+    pub use foo::Foo;
+}
+
+// @count private_twice_one_inline.json "$.index[*][?(@.kind=='import')]" 2
diff --git a/src/test/rustdoc-json/reexport/private_two_names.rs b/src/test/rustdoc-json/reexport/private_two_names.rs
new file mode 100644
index 0000000000000..36d6a50d385a2
--- /dev/null
+++ b/src/test/rustdoc-json/reexport/private_two_names.rs
@@ -0,0 +1,17 @@
+// Test for the ICE in rust/83720
+// A pub-in-private type re-exported under two different names shouldn't cause an error
+
+#![no_core]
+#![feature(no_core)]
+
+// @is private_two_names.json "$.index[*][?(@.name=='style')].kind" \"module\"
+// @is private_two_names.json "$.index[*][?(@.name=='style')].inner.is_stripped" "true"
+mod style {
+    // @has - "$.index[*](?(@.name=='Color'))"
+    pub struct Color;
+}
+
+// @has - "$.index[*][?(@.kind=='import' && @.inner.name=='Color')]"
+pub use style::Color;
+// @has - "$.index[*][?(@.kind=='import' && @.inner.name=='Colour')]"
+pub use style::Color as Colour;
diff --git a/src/test/rustdoc-json/reexport/rename_private.rs b/src/test/rustdoc-json/reexport/rename_private.rs
index fb8296f23374a..2476399bd561c 100644
--- a/src/test/rustdoc-json/reexport/rename_private.rs
+++ b/src/test/rustdoc-json/reexport/rename_private.rs
@@ -2,13 +2,13 @@
 
 #![no_core]
 #![feature(no_core)]
-// @!has rename_private.json "$.index[*][?(@.name=='inner')]"
+
+// @is rename_private.json "$.index[*][?(@.name=='inner')].kind" \"module\"
+// @is rename_private.json "$.index[*][?(@.name=='inner')].inner.is_stripped" "true"
 mod inner {
-    // @!has - "$.index[*][?(@.name=='Public')]"
+    // @has - "$.index[*][?(@.name=='Public')]"
     pub struct Public;
 }
 
-// @set newname_id = - "$.index[*][?(@.name=='NewName')].id"
-// @is - "$.index[*][?(@.name=='NewName')].kind" \"struct\"
-// @has - "$.index[*][?(@.name=='rename_private')].inner.items[*]" $newname_id
+// @is - "$.index[*][?(@.kind=='import')].inner.name" \"NewName\"
 pub use inner::Public as NewName;
diff --git a/src/test/rustdoc-json/reexport/same_type_reexported_more_than_once.rs b/src/test/rustdoc-json/reexport/same_type_reexported_more_than_once.rs
index fd6ac8372d976..eedddd6a7bb48 100644
--- a/src/test/rustdoc-json/reexport/same_type_reexported_more_than_once.rs
+++ b/src/test/rustdoc-json/reexport/same_type_reexported_more_than_once.rs
@@ -1,15 +1,13 @@
-// Regression test for https://github.com/rust-lang/rust/issues/97432.
+// Regression test for <https://github.com/rust-lang/rust/issues/97432>.
 
 #![feature(no_core)]
 #![no_std]
 #![no_core]
 
 // @has same_type_reexported_more_than_once.json
-// @set trait_id = - "$.index[*][?(@.name=='Trait')].id"
-// @has - "$.index[*][?(@.name=='same_type_reexported_more_than_once')].inner.items[*]" $trait_id
+// @has - "$.index[*][?(@.name=='Trait')]"
 pub use inner::Trait;
-// @set reexport_id = - "$.index[*][?(@.name=='Reexport')].id"
-// @has - "$.index[*][?(@.name=='same_type_reexported_more_than_once')].inner.items[*]" $reexport_id
+// @has - "$.index[*].inner[?(@.name=='Reexport')].id"
 pub use inner::Trait as Reexport;
 
 mod inner {
diff --git a/src/test/rustdoc-json/reexport/simple_private.rs b/src/test/rustdoc-json/reexport/simple_private.rs
index 658b121e6ce97..5ec13e403aef6 100644
--- a/src/test/rustdoc-json/reexport/simple_private.rs
+++ b/src/test/rustdoc-json/reexport/simple_private.rs
@@ -1,13 +1,15 @@
 // edition:2018
-
 #![no_core]
 #![feature(no_core)]
 
-// @!has simple_private.json "$.index[*][?(@.name=='inner')]"
+// @is simple_private.json "$.index[*][?(@.name=='inner')].kind" \"module\"
+// @is simple_private.json "$.index[*][?(@.name=='inner')].inner.is_stripped" "true"
 mod inner {
     // @set pub_id = - "$.index[*][?(@.name=='Public')].id"
     pub struct Public;
 }
 
-// @has - "$.index[*][?(@.name=='simple_private')].inner.items[*]" $pub_id
+// @is - "$.index[*][?(@.kind=='import')].inner.name" \"Public\"
 pub use inner::Public;
+
+// @has - "$.index[*][?(@.name=='inner')].inner.items[*]" $pub_id
diff --git a/src/test/rustdoc-json/return_private.rs b/src/test/rustdoc-json/return_private.rs
new file mode 100644
index 0000000000000..6b324d0090a15
--- /dev/null
+++ b/src/test/rustdoc-json/return_private.rs
@@ -0,0 +1,15 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/96161>.
+// ignore-tidy-linelength
+
+#![feature(no_core)]
+#![no_core]
+
+mod secret {
+    pub struct Secret;
+}
+
+// @is return_private.json "$.index[*][?(@.name=='get_secret')].kind" \"function\"
+// @is return_private.json "$.index[*][?(@.name=='get_secret')].inner.decl.output.inner.name" \"secret::Secret\"
+pub fn get_secret() -> secret::Secret {
+    secret::Secret
+}
diff --git a/src/test/rustdoc-json/stripped_modules.rs b/src/test/rustdoc-json/stripped_modules.rs
new file mode 100644
index 0000000000000..91f9f02ad7b47
--- /dev/null
+++ b/src/test/rustdoc-json/stripped_modules.rs
@@ -0,0 +1,21 @@
+#![no_core]
+#![feature(no_core)]
+
+// @!has stripped_modules.json "$.index[*][?(@.name=='no_pub_inner')]"
+mod no_pub_inner {
+    fn priv_inner() {}
+}
+
+// @!has - "$.index[*][?(@.name=='pub_inner_unreachable')]"
+mod pub_inner_unreachable {
+    // @!has - "$.index[*][?(@.name=='pub_inner_1')]"
+    pub fn pub_inner_1() {}
+}
+
+// @has - "$.index[*][?(@.name=='pub_inner_reachable')]"
+mod pub_inner_reachable {
+    // @has - "$.index[*][?(@.name=='pub_inner_2')]"
+    pub fn pub_inner_2() {}
+}
+
+pub use pub_inner_reachable::pub_inner_2;
diff --git a/src/test/rustdoc-ui/invalid-doc-attr.stderr b/src/test/rustdoc-ui/invalid-doc-attr.stderr
index 55006b2087eb0..a4fa3817905c7 100644
--- a/src/test/rustdoc-ui/invalid-doc-attr.stderr
+++ b/src/test/rustdoc-ui/invalid-doc-attr.stderr
@@ -12,7 +12,7 @@ LL | #![deny(warnings)]
    = note: `#[deny(invalid_doc_attributes)]` implied by `#[deny(warnings)]`
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82730 <https://github.com/rust-lang/rust/issues/82730>
-   = note: read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level for more information
+   = note: read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level> for more information
 help: to apply to the crate, use an inner attribute
    |
 LL | #![doc(test(no_crate_inject))]
@@ -29,7 +29,7 @@ LL | pub fn foo() {}
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82730 <https://github.com/rust-lang/rust/issues/82730>
-   = note: read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#inline-and-no_inline for more information
+   = note: read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#inline-and-no_inline> for more information
 
 error: this attribute can only be applied at the crate level
   --> $DIR/invalid-doc-attr.rs:15:12
@@ -39,7 +39,7 @@ LL |     #![doc(test(no_crate_inject))]
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82730 <https://github.com/rust-lang/rust/issues/82730>
-   = note: read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level for more information
+   = note: read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level> for more information
 
 error: conflicting doc inlining attributes
   --> $DIR/invalid-doc-attr.rs:28:7
@@ -59,7 +59,7 @@ LL |     #[doc(test(no_crate_inject))]
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82730 <https://github.com/rust-lang/rust/issues/82730>
-   = note: read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level for more information
+   = note: read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level> for more information
 
 error: this attribute can only be applied to a `use` item
   --> $DIR/invalid-doc-attr.rs:22:11
@@ -72,7 +72,7 @@ LL |     pub fn baz() {}
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82730 <https://github.com/rust-lang/rust/issues/82730>
-   = note: read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#inline-and-no_inline for more information
+   = note: read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#inline-and-no_inline> for more information
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/ui-fulldeps/session-diagnostic/diagnostic-derive.rs b/src/test/ui-fulldeps/session-diagnostic/diagnostic-derive.rs
index 56e95d70fd53d..0a210cbdc9430 100644
--- a/src/test/ui-fulldeps/session-diagnostic/diagnostic-derive.rs
+++ b/src/test/ui-fulldeps/session-diagnostic/diagnostic-derive.rs
@@ -23,7 +23,7 @@ extern crate rustc_middle;
 use rustc_middle::ty::Ty;
 
 extern crate rustc_errors;
-use rustc_errors::Applicability;
+use rustc_errors::{Applicability, MultiSpan};
 
 extern crate rustc_session;
 
@@ -140,7 +140,7 @@ struct CodeNotProvided {}
 #[error(typeck::ambiguous_lifetime_bound, code = "E0123")]
 struct MessageWrongType {
     #[primary_span]
-    //~^ ERROR `#[primary_span]` attribute can only be applied to fields of type `Span`
+    //~^ ERROR `#[primary_span]` attribute can only be applied to fields of type `Span` or `MultiSpan`
     foo: String,
 }
 
@@ -165,7 +165,7 @@ struct ErrorWithField {
 #[error(typeck::ambiguous_lifetime_bound, code = "E0123")]
 struct ErrorWithMessageAppliedToField {
     #[label(typeck::label)]
-    //~^ ERROR the `#[label(...)]` attribute can only be applied to fields of type `Span`
+    //~^ ERROR the `#[label(...)]` attribute can only be applied to fields of type `Span` or `MultiSpan`
     name: String,
 }
 
@@ -208,7 +208,7 @@ struct LabelOnSpan {
 #[error(typeck::ambiguous_lifetime_bound, code = "E0123")]
 struct LabelOnNonSpan {
     #[label(typeck::label)]
-    //~^ ERROR the `#[label(...)]` attribute can only be applied to fields of type `Span`
+    //~^ ERROR the `#[label(...)]` attribute can only be applied to fields of type `Span` or `MultiSpan`
     id: u32,
 }
 
@@ -538,7 +538,7 @@ struct LabelWithTrailingList {
 
 #[derive(SessionDiagnostic)]
 #[lint(typeck::ambiguous_lifetime_bound)]
-//~^ ERROR only `#[error(..)]` and `#[warn(..)]` are supported
+//~^ ERROR only `#[error(..)]` and `#[warning(..)]` are supported
 struct LintsBad {
 }
 
@@ -552,3 +552,17 @@ struct LintsGood {
 //~^ ERROR only `#[lint(..)]` is supported
 struct ErrorsBad {
 }
+
+#[derive(SessionDiagnostic)]
+#[error(typeck::ambiguous_lifetime_bound, code = "E0123")]
+struct ErrorWithMultiSpan {
+    #[primary_span]
+    span: MultiSpan,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(typeck::ambiguous_lifetime_bound, code = "E0123")]
+#[warn_]
+struct ErrorWithWarn {
+    val: String,
+}
diff --git a/src/test/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr b/src/test/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr
index e282884289db3..c1080aa24521f 100644
--- a/src/test/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr
+++ b/src/test/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr
@@ -21,7 +21,7 @@ error: `#[nonsense(...)]` is not a valid attribute
 LL | #[nonsense(typeck::ambiguous_lifetime_bound, code = "E0123")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: only `error`, `warning`, `help` and `note` are valid attributes
+   = help: only `error`, `warning`, `help`, `note` and `warn_` are valid attributes
 
 error: diagnostic kind not specified
   --> $DIR/diagnostic-derive.rs:53:1
@@ -233,7 +233,7 @@ LL | | struct SlugNotProvided {}
    |
    = help: specify the slug as the first argument to the attribute, such as `#[error(typeck::example_error)]`
 
-error: the `#[primary_span]` attribute can only be applied to fields of type `Span`
+error: the `#[primary_span]` attribute can only be applied to fields of type `Span` or `MultiSpan`
   --> $DIR/diagnostic-derive.rs:142:5
    |
 LL |     #[primary_span]
@@ -247,7 +247,7 @@ LL |     #[nonsense]
    |
    = help: only `skip_arg`, `primary_span`, `label`, `note`, `help` and `subdiagnostic` are valid field attributes
 
-error: the `#[label(...)]` attribute can only be applied to fields of type `Span`
+error: the `#[label(...)]` attribute can only be applied to fields of type `Span` or `MultiSpan`
   --> $DIR/diagnostic-derive.rs:167:5
    |
 LL |     #[label(typeck::label)]
@@ -279,7 +279,7 @@ LL | #[derive(SessionDiagnostic)]
    = note: if you intended to print `}`, you can escape it using `}}`
    = note: this error originates in the derive macro `SessionDiagnostic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: the `#[label(...)]` attribute can only be applied to fields of type `Span`
+error: the `#[label(...)]` attribute can only be applied to fields of type `Span` or `MultiSpan`
   --> $DIR/diagnostic-derive.rs:210:5
    |
 LL |     #[label(typeck::label)]
@@ -363,7 +363,7 @@ error: `#[label(...)]` is not a valid attribute
 LL |     #[label(typeck::label, foo("..."))]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: only `#[error(..)]` and `#[warn(..)]` are supported
+error: only `#[error(..)]` and `#[warning(..)]` are supported
   --> $DIR/diagnostic-derive.rs:540:1
    |
 LL | / #[lint(typeck::ambiguous_lifetime_bound)]
diff --git a/src/test/ui-fulldeps/session-diagnostic/subdiagnostic-derive.rs b/src/test/ui-fulldeps/session-diagnostic/subdiagnostic-derive.rs
index 6f4b6105b3e49..16da25c402b57 100644
--- a/src/test/ui-fulldeps/session-diagnostic/subdiagnostic-derive.rs
+++ b/src/test/ui-fulldeps/session-diagnostic/subdiagnostic-derive.rs
@@ -244,7 +244,7 @@ enum V {
 //~^ ERROR label without `#[primary_span]` field
 struct W {
     #[primary_span]
-    //~^ ERROR the `#[primary_span]` attribute can only be applied to fields of type `Span`
+    //~^ ERROR the `#[primary_span]` attribute can only be applied to fields of type `Span` or `MultiSpan`
     span: String,
 }
 
@@ -508,3 +508,15 @@ enum AX {
         span: Span,
     }
 }
+
+#[derive(SessionSubdiagnostic)]
+#[warn_(parser::add_paren)]
+struct AY {
+}
+
+#[derive(SessionSubdiagnostic)]
+#[warn_(parser::add_paren)]
+struct AZ {
+    #[primary_span]
+    span: Span,
+}
diff --git a/src/test/ui-fulldeps/session-diagnostic/subdiagnostic-derive.stderr b/src/test/ui-fulldeps/session-diagnostic/subdiagnostic-derive.stderr
index f833bd210f7f5..a289c4fffd936 100644
--- a/src/test/ui-fulldeps/session-diagnostic/subdiagnostic-derive.stderr
+++ b/src/test/ui-fulldeps/session-diagnostic/subdiagnostic-derive.stderr
@@ -120,7 +120,7 @@ error: subdiagnostic kind not specified
 LL |     B {
    |     ^
 
-error: the `#[primary_span]` attribute can only be applied to fields of type `Span`
+error: the `#[primary_span]` attribute can only be applied to fields of type `Span` or `MultiSpan`
   --> $DIR/subdiagnostic-derive.rs:246:5
    |
 LL |     #[primary_span]
diff --git a/src/test/ui/attributes/invalid-doc-attr.stderr b/src/test/ui/attributes/invalid-doc-attr.stderr
index 55006b2087eb0..a4fa3817905c7 100644
--- a/src/test/ui/attributes/invalid-doc-attr.stderr
+++ b/src/test/ui/attributes/invalid-doc-attr.stderr
@@ -12,7 +12,7 @@ LL | #![deny(warnings)]
    = note: `#[deny(invalid_doc_attributes)]` implied by `#[deny(warnings)]`
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82730 <https://github.com/rust-lang/rust/issues/82730>
-   = note: read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level for more information
+   = note: read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level> for more information
 help: to apply to the crate, use an inner attribute
    |
 LL | #![doc(test(no_crate_inject))]
@@ -29,7 +29,7 @@ LL | pub fn foo() {}
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82730 <https://github.com/rust-lang/rust/issues/82730>
-   = note: read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#inline-and-no_inline for more information
+   = note: read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#inline-and-no_inline> for more information
 
 error: this attribute can only be applied at the crate level
   --> $DIR/invalid-doc-attr.rs:15:12
@@ -39,7 +39,7 @@ LL |     #![doc(test(no_crate_inject))]
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82730 <https://github.com/rust-lang/rust/issues/82730>
-   = note: read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level for more information
+   = note: read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level> for more information
 
 error: conflicting doc inlining attributes
   --> $DIR/invalid-doc-attr.rs:28:7
@@ -59,7 +59,7 @@ LL |     #[doc(test(no_crate_inject))]
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82730 <https://github.com/rust-lang/rust/issues/82730>
-   = note: read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level for more information
+   = note: read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level> for more information
 
 error: this attribute can only be applied to a `use` item
   --> $DIR/invalid-doc-attr.rs:22:11
@@ -72,7 +72,7 @@ LL |     pub fn baz() {}
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82730 <https://github.com/rust-lang/rust/issues/82730>
-   = note: read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#inline-and-no_inline for more information
+   = note: read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#inline-and-no_inline> for more information
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/ui/attributes/multiple-invalid.stderr b/src/test/ui/attributes/multiple-invalid.stderr
index 9bd29f15dbcca..a8dba0ba37d3a 100644
--- a/src/test/ui/attributes/multiple-invalid.stderr
+++ b/src/test/ui/attributes/multiple-invalid.stderr
@@ -7,14 +7,14 @@ LL | #[inline]
 LL | const FOO: u8 = 0;
    | ------------------ not a function or closure
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/multiple-invalid.rs:6:1
    |
 LL | #[target_feature(enable = "sse2")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
 LL | const FOO: u8 = 0;
-   | ------------------ not a function
+   | ------------------ not a function definition
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/borrowck/borrowck-borrowed-uniq-rvalue.fixed b/src/test/ui/borrowck/borrowck-borrowed-uniq-rvalue.fixed
new file mode 100644
index 0000000000000..8bf6a2f6db396
--- /dev/null
+++ b/src/test/ui/borrowck/borrowck-borrowed-uniq-rvalue.fixed
@@ -0,0 +1,14 @@
+// run-rustfix
+
+use std::collections::HashMap;
+
+fn main() {
+    let tmp: Box<_>;
+    let mut buggy_map: HashMap<usize, &usize> = HashMap::new();
+    let binding = Box::new(1);
+    buggy_map.insert(42, &*binding); //~ ERROR temporary value dropped while borrowed
+
+    // but it is ok if we use a temporary
+    tmp = Box::new(2);
+    buggy_map.insert(43, &*tmp);
+}
diff --git a/src/test/ui/borrowck/borrowck-borrowed-uniq-rvalue.rs b/src/test/ui/borrowck/borrowck-borrowed-uniq-rvalue.rs
index 1d05845fc6b20..85481336a305f 100644
--- a/src/test/ui/borrowck/borrowck-borrowed-uniq-rvalue.rs
+++ b/src/test/ui/borrowck/borrowck-borrowed-uniq-rvalue.rs
@@ -1,8 +1,6 @@
-use std::collections::HashMap;
-
-
-
+// run-rustfix
 
+use std::collections::HashMap;
 
 fn main() {
     let tmp: Box<_>;
diff --git a/src/test/ui/borrowck/borrowck-borrowed-uniq-rvalue.stderr b/src/test/ui/borrowck/borrowck-borrowed-uniq-rvalue.stderr
index 01379ed851200..dea8ac90bec2e 100644
--- a/src/test/ui/borrowck/borrowck-borrowed-uniq-rvalue.stderr
+++ b/src/test/ui/borrowck/borrowck-borrowed-uniq-rvalue.stderr
@@ -1,5 +1,5 @@
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/borrowck-borrowed-uniq-rvalue.rs:10:28
+  --> $DIR/borrowck-borrowed-uniq-rvalue.rs:8:28
    |
 LL |     buggy_map.insert(42, &*Box::new(1));
    |                            ^^^^^^^^^^^ - temporary value is freed at the end of this statement
@@ -9,7 +9,11 @@ LL |     buggy_map.insert(42, &*Box::new(1));
 LL |     buggy_map.insert(43, &*tmp);
    |     --------------------------- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = Box::new(1);
+LL ~     buggy_map.insert(42, &*binding);
+   |
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/issue-11493.fixed b/src/test/ui/borrowck/issue-11493.fixed
new file mode 100644
index 0000000000000..139bd9a073973
--- /dev/null
+++ b/src/test/ui/borrowck/issue-11493.fixed
@@ -0,0 +1,9 @@
+// run-rustfix
+fn id<T>(x: T) -> T { x }
+
+fn main() {
+    let x = Some(3);
+    let binding = id(5);
+    let y = x.as_ref().unwrap_or(&binding);  //~ ERROR
+    let _ = &y;
+}
diff --git a/src/test/ui/issues/issue-11493.rs b/src/test/ui/borrowck/issue-11493.rs
similarity index 78%
rename from src/test/ui/issues/issue-11493.rs
rename to src/test/ui/borrowck/issue-11493.rs
index b28c173b19b71..cb77f89fb2b1e 100644
--- a/src/test/ui/issues/issue-11493.rs
+++ b/src/test/ui/borrowck/issue-11493.rs
@@ -1,7 +1,8 @@
+// run-rustfix
 fn id<T>(x: T) -> T { x }
 
 fn main() {
     let x = Some(3);
     let y = x.as_ref().unwrap_or(&id(5));  //~ ERROR
-    &y;
+    let _ = &y;
 }
diff --git a/src/test/ui/issues/issue-11493.stderr b/src/test/ui/borrowck/issue-11493.stderr
similarity index 64%
rename from src/test/ui/issues/issue-11493.stderr
rename to src/test/ui/borrowck/issue-11493.stderr
index f954d64ac5bf4..a5d1f2816f1ca 100644
--- a/src/test/ui/issues/issue-11493.stderr
+++ b/src/test/ui/borrowck/issue-11493.stderr
@@ -1,14 +1,18 @@
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/issue-11493.rs:5:35
+  --> $DIR/issue-11493.rs:6:35
    |
 LL |     let y = x.as_ref().unwrap_or(&id(5));
    |                                   ^^^^^ - temporary value is freed at the end of this statement
    |                                   |
    |                                   creates a temporary which is freed while still in use
-LL |     &y;
-   |     -- borrow later used here
+LL |     let _ = &y;
+   |             -- borrow later used here
+   |
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = id(5);
+LL ~     let y = x.as_ref().unwrap_or(&binding);
    |
-   = note: consider using a `let` binding to create a longer lived value
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/issue-36082.fixed b/src/test/ui/borrowck/issue-36082.fixed
new file mode 100644
index 0000000000000..8640ca7a50964
--- /dev/null
+++ b/src/test/ui/borrowck/issue-36082.fixed
@@ -0,0 +1,17 @@
+// run-rustfix
+use std::cell::RefCell;
+
+fn main() {
+    let mut r = 0;
+    let s = 0;
+    let x = RefCell::new((&mut r,s));
+
+    let binding = x.borrow();
+    let val: &_ = binding.0;
+    //~^ ERROR temporary value dropped while borrowed [E0716]
+    //~| NOTE temporary value is freed at the end of this statement
+    //~| NOTE creates a temporary which is freed while still in use
+    //~| HELP consider using a `let` binding to create a longer lived value
+    println!("{}", val);
+    //~^ borrow later used here
+}
diff --git a/src/test/ui/issues/issue-36082.rs b/src/test/ui/borrowck/issue-36082.rs
similarity index 83%
rename from src/test/ui/issues/issue-36082.rs
rename to src/test/ui/borrowck/issue-36082.rs
index a2ff477eb816a..877d372fb8484 100644
--- a/src/test/ui/issues/issue-36082.rs
+++ b/src/test/ui/borrowck/issue-36082.rs
@@ -1,3 +1,4 @@
+// run-rustfix
 use std::cell::RefCell;
 
 fn main() {
@@ -9,7 +10,7 @@ fn main() {
     //~^ ERROR temporary value dropped while borrowed [E0716]
     //~| NOTE temporary value is freed at the end of this statement
     //~| NOTE creates a temporary which is freed while still in use
-    //~| NOTE consider using a `let` binding to create a longer lived value
+    //~| HELP consider using a `let` binding to create a longer lived value
     println!("{}", val);
     //~^ borrow later used here
 }
diff --git a/src/test/ui/issues/issue-36082.stderr b/src/test/ui/borrowck/issue-36082.stderr
similarity index 73%
rename from src/test/ui/issues/issue-36082.stderr
rename to src/test/ui/borrowck/issue-36082.stderr
index 26bf4cb1be8be..4bd586db1cdce 100644
--- a/src/test/ui/issues/issue-36082.stderr
+++ b/src/test/ui/borrowck/issue-36082.stderr
@@ -1,5 +1,5 @@
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/issue-36082.rs:8:19
+  --> $DIR/issue-36082.rs:9:19
    |
 LL |     let val: &_ = x.borrow().0;
    |                   ^^^^^^^^^^  - temporary value is freed at the end of this statement
@@ -9,7 +9,11 @@ LL |     let val: &_ = x.borrow().0;
 LL |     println!("{}", val);
    |                    --- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = x.borrow();
+LL ~     let val: &_ = binding.0;
+   |
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/cleanup-rvalue-scopes-cf.stderr b/src/test/ui/cleanup-rvalue-scopes-cf.stderr
index 04e599755fb29..40f14c389842e 100644
--- a/src/test/ui/cleanup-rvalue-scopes-cf.stderr
+++ b/src/test/ui/cleanup-rvalue-scopes-cf.stderr
@@ -9,7 +9,11 @@ LL |     let x1 = arg(&AddFlags(1));
 LL |     (x1, x2, x3, x4, x5, x6, x7);
    |      -- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = AddFlags(1);
+LL ~     let x1 = arg(&binding);
+   |
 
 error[E0716]: temporary value dropped while borrowed
   --> $DIR/cleanup-rvalue-scopes-cf.rs:27:14
@@ -22,7 +26,11 @@ LL |     let x2 = AddFlags(1).get();
 LL |     (x1, x2, x3, x4, x5, x6, x7);
    |          -- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = AddFlags(1);
+LL ~     let x2 = binding.get();
+   |
 
 error[E0716]: temporary value dropped while borrowed
   --> $DIR/cleanup-rvalue-scopes-cf.rs:28:21
@@ -35,7 +43,11 @@ LL |     let x3 = &*arg(&AddFlags(1));
 LL |     (x1, x2, x3, x4, x5, x6, x7);
    |              -- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = AddFlags(1);
+LL ~     let x3 = &*arg(&binding);
+   |
 
 error[E0716]: temporary value dropped while borrowed
   --> $DIR/cleanup-rvalue-scopes-cf.rs:29:24
@@ -48,7 +60,11 @@ LL |     let ref x4 = *arg(&AddFlags(1));
 LL |     (x1, x2, x3, x4, x5, x6, x7);
    |                  -- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = AddFlags(1);
+LL ~     let ref x4 = *arg(&binding);
+   |
 
 error[E0716]: temporary value dropped while borrowed
   --> $DIR/cleanup-rvalue-scopes-cf.rs:30:24
@@ -61,7 +77,11 @@ LL |     let &ref x5 = arg(&AddFlags(1));
 LL |     (x1, x2, x3, x4, x5, x6, x7);
    |                      -- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = AddFlags(1);
+LL ~     let &ref x5 = arg(&binding);
+   |
 
 error[E0716]: temporary value dropped while borrowed
   --> $DIR/cleanup-rvalue-scopes-cf.rs:31:14
@@ -74,7 +94,11 @@ LL |     let x6 = AddFlags(1).get();
 LL |     (x1, x2, x3, x4, x5, x6, x7);
    |                          -- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = AddFlags(1);
+LL ~     let x6 = binding.get();
+   |
 
 error[E0716]: temporary value dropped while borrowed
   --> $DIR/cleanup-rvalue-scopes-cf.rs:32:44
@@ -87,7 +111,11 @@ LL |
 LL |     (x1, x2, x3, x4, x5, x6, x7);
    |                              -- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = AddFlags(1);
+LL ~     let StackBox { f: x7 } = StackBox { f: binding.get() };
+   |
 
 error: aborting due to 7 previous errors
 
diff --git a/src/test/ui/feature-gates/issue-43106-gating-of-builtin-attrs.stderr b/src/test/ui/feature-gates/issue-43106-gating-of-builtin-attrs.stderr
index 3f838fcf52355..5d6796b49448a 100644
--- a/src/test/ui/feature-gates/issue-43106-gating-of-builtin-attrs.stderr
+++ b/src/test/ui/feature-gates/issue-43106-gating-of-builtin-attrs.stderr
@@ -259,7 +259,7 @@ warning: crate-level attribute should be an inner attribute: add an exclamation
 LL | #[no_std]
    | ^^^^^^^^^
 
-warning: attribute should be applied to a function
+warning: attribute should be applied to a function definition
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:453:1
    |
 LL |   #[cold]
@@ -272,7 +272,7 @@ LL | |     mod inner { #![cold] }
 ...  |
 LL | |
 LL | | }
-   | |_- not a function
+   | |_- not a function definition
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 
@@ -399,7 +399,7 @@ warning: `#[proc_macro_derive]` only has an effect on functions
 LL | #![proc_macro_derive()]
    | ^^^^^^^^^^^^^^^^^^^^^^^
 
-warning: attribute should be applied to a function
+warning: attribute should be applied to a function definition
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:62:1
    |
 LL | #![cold]
@@ -743,35 +743,35 @@ warning: crate-level attribute should be an inner attribute: add an exclamation
 LL |     #[no_std] impl S { }
    |     ^^^^^^^^^
 
-warning: attribute should be applied to a function
+warning: attribute should be applied to a function definition
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:459:17
    |
 LL |     mod inner { #![cold] }
-   |     ------------^^^^^^^^-- not a function
+   |     ------------^^^^^^^^-- not a function definition
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 
-warning: attribute should be applied to a function
+warning: attribute should be applied to a function definition
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:466:5
    |
 LL |     #[cold] struct S;
-   |     ^^^^^^^ --------- not a function
+   |     ^^^^^^^ --------- not a function definition
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 
-warning: attribute should be applied to a function
+warning: attribute should be applied to a function definition
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:471:5
    |
 LL |     #[cold] type T = S;
-   |     ^^^^^^^ ----------- not a function
+   |     ^^^^^^^ ----------- not a function definition
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 
-warning: attribute should be applied to a function
+warning: attribute should be applied to a function definition
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:476:5
    |
 LL |     #[cold] impl S { }
-   |     ^^^^^^^ ---------- not a function
+   |     ^^^^^^^ ---------- not a function definition
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 
diff --git a/src/test/ui/future-incompatible-lint-group.stderr b/src/test/ui/future-incompatible-lint-group.stderr
index d822847a7a589..8f6dde665e628 100644
--- a/src/test/ui/future-incompatible-lint-group.stderr
+++ b/src/test/ui/future-incompatible-lint-group.stderr
@@ -22,7 +22,7 @@ LL | #![deny(future_incompatible)]
    = note: `#[deny(invalid_doc_attributes)]` implied by `#[deny(future_incompatible)]`
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82730 <https://github.com/rust-lang/rust/issues/82730>
-   = note: read https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level for more information
+   = note: read <https://doc.rust-lang.org/nightly/rustdoc/the-doc-attribute.html#at-the-crate-level> for more information
 
 error: aborting due to previous error; 1 warning emitted
 
diff --git a/src/test/ui/issues/issue-21974.stderr b/src/test/ui/issues/issue-21974.stderr
index 2d60b18b1f208..4e010a13653e7 100644
--- a/src/test/ui/issues/issue-21974.stderr
+++ b/src/test/ui/issues/issue-21974.stderr
@@ -4,13 +4,7 @@ error[E0283]: type annotations needed: cannot satisfy `&'a T: Foo`
 LL |     where &'a T : Foo,
    |                   ^^^
    |
-note: multiple `impl`s or `where` clauses satisfying `&'a T: Foo` found
-  --> $DIR/issue-21974.rs:11:19
-   |
-LL |     where &'a T : Foo,
-   |                   ^^^
-LL |           &'b T : Foo
-   |                   ^^^
+   = note: cannot satisfy `&'a T: Foo`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-24424.stderr b/src/test/ui/issues/issue-24424.stderr
index 50d7f988e194c..8f3b2ac73199c 100644
--- a/src/test/ui/issues/issue-24424.stderr
+++ b/src/test/ui/issues/issue-24424.stderr
@@ -4,11 +4,7 @@ error[E0283]: type annotations needed: cannot satisfy `T0: Trait0<'l0>`
 LL | impl <'l0, 'l1, T0> Trait1<'l0, T0> for bool where T0 : Trait0<'l0>, T0 : Trait0<'l1> {}
    |                                                         ^^^^^^^^^^^
    |
-note: multiple `impl`s or `where` clauses satisfying `T0: Trait0<'l0>` found
-  --> $DIR/issue-24424.rs:4:57
-   |
-LL | impl <'l0, 'l1, T0> Trait1<'l0, T0> for bool where T0 : Trait0<'l0>, T0 : Trait0<'l1> {}
-   |                                                         ^^^^^^^^^^^       ^^^^^^^^^^^
+   = note: cannot satisfy `T0: Trait0<'l0>`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-54044.stderr b/src/test/ui/issues/issue-54044.stderr
index 0200a6a629d8f..100965de1aa84 100644
--- a/src/test/ui/issues/issue-54044.stderr
+++ b/src/test/ui/issues/issue-54044.stderr
@@ -1,11 +1,11 @@
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/issue-54044.rs:3:1
    |
 LL | #[cold]
    | ^^^^^^^
 ...
 LL | struct Foo;
-   | ----------- not a function
+   | ----------- not a function definition
    |
 note: the lint level is defined here
   --> $DIR/issue-54044.rs:1:9
@@ -14,14 +14,14 @@ LL | #![deny(unused_attributes)]
    |         ^^^^^^^^^^^^^^^^^
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/issue-54044.rs:9:5
    |
 LL |     #[cold]
    |     ^^^^^^^
 ...
 LL |     5;
-   |     - not a function
+   |     - not a function definition
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 
diff --git a/src/test/ui/issues/issue-78957.stderr b/src/test/ui/issues/issue-78957.stderr
index fa2eaab5b417b..45fa69d6fd708 100644
--- a/src/test/ui/issues/issue-78957.stderr
+++ b/src/test/ui/issues/issue-78957.stderr
@@ -4,11 +4,11 @@ error[E0518]: attribute should be applied to function or closure
 LL | pub struct Foo<#[inline] const N: usize>;
    |                ^^^^^^^^^ -------------- not a function or closure
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/issue-78957.rs:7:16
    |
 LL | pub struct Bar<#[cold] const N: usize>;
-   |                ^^^^^^^ -------------- not a function
+   |                ^^^^^^^ -------------- not a function definition
    |
 note: the lint level is defined here
   --> $DIR/issue-78957.rs:1:9
@@ -29,11 +29,11 @@ error[E0518]: attribute should be applied to function or closure
 LL | pub struct Foo2<#[inline] 'a>(PhantomData<&'a ()>);
    |                 ^^^^^^^^^ -- not a function or closure
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/issue-78957.rs:15:17
    |
 LL | pub struct Bar2<#[cold] 'a>(PhantomData<&'a ()>);
-   |                 ^^^^^^^ -- not a function
+   |                 ^^^^^^^ -- not a function definition
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 
@@ -49,11 +49,11 @@ error[E0518]: attribute should be applied to function or closure
 LL | pub struct Foo3<#[inline] T>(PhantomData<T>);
    |                 ^^^^^^^^^ - not a function or closure
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/issue-78957.rs:23:17
    |
 LL | pub struct Bar3<#[cold] T>(PhantomData<T>);
-   |                 ^^^^^^^ - not a function
+   |                 ^^^^^^^ - not a function definition
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 
diff --git a/src/test/ui/lifetimes/issue-34979.stderr b/src/test/ui/lifetimes/issue-34979.stderr
index a78b3eaf6258d..5832c4d173c10 100644
--- a/src/test/ui/lifetimes/issue-34979.stderr
+++ b/src/test/ui/lifetimes/issue-34979.stderr
@@ -4,13 +4,7 @@ error[E0283]: type annotations needed: cannot satisfy `&'a (): Foo`
 LL |     &'a (): Foo,
    |             ^^^
    |
-note: multiple `impl`s or `where` clauses satisfying `&'a (): Foo` found
-  --> $DIR/issue-34979.rs:6:13
-   |
-LL |     &'a (): Foo,
-   |             ^^^
-LL |     &'static (): Foo;
-   |                  ^^^
+   = note: cannot satisfy `&'a (): Foo`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/macros/issue-68060.stderr b/src/test/ui/macros/issue-68060.stderr
index 1b58cf9c4ede5..b13e418e664a6 100644
--- a/src/test/ui/macros/issue-68060.stderr
+++ b/src/test/ui/macros/issue-68060.stderr
@@ -1,11 +1,11 @@
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/issue-68060.rs:4:13
    |
 LL |             #[target_feature(enable = "")]
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 ...
 LL |             |_| (),
-   |             ------ not a function
+   |             ------ not a function definition
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/marker_trait_attr/marker-attribute-on-non-trait.rs b/src/test/ui/marker_trait_attr/marker-attribute-on-non-trait.rs
index 66156b6e53bab..0bf620934ec7b 100644
--- a/src/test/ui/marker_trait_attr/marker-attribute-on-non-trait.rs
+++ b/src/test/ui/marker_trait_attr/marker-attribute-on-non-trait.rs
@@ -1,23 +1,23 @@
 #![feature(marker_trait_attr)]
 
-#[marker] //~ ERROR attribute can only be applied to a trait
+#[marker] //~ ERROR attribute should be applied to a trait
 struct Struct {}
 
-#[marker] //~ ERROR attribute can only be applied to a trait
+#[marker] //~ ERROR attribute should be applied to a trait
 impl Struct {}
 
-#[marker] //~ ERROR attribute can only be applied to a trait
+#[marker] //~ ERROR attribute should be applied to a trait
 union Union {
     x: i32,
 }
 
-#[marker] //~ ERROR attribute can only be applied to a trait
+#[marker] //~ ERROR attribute should be applied to a trait
 const CONST: usize = 10;
 
-#[marker] //~ ERROR attribute can only be applied to a trait
+#[marker] //~ ERROR attribute should be applied to a trait
 fn function() {}
 
-#[marker] //~ ERROR attribute can only be applied to a trait
+#[marker] //~ ERROR attribute should be applied to a trait
 type Type = ();
 
 fn main() {}
diff --git a/src/test/ui/marker_trait_attr/marker-attribute-on-non-trait.stderr b/src/test/ui/marker_trait_attr/marker-attribute-on-non-trait.stderr
index d30b990caac2b..19a5290dd7eb6 100644
--- a/src/test/ui/marker_trait_attr/marker-attribute-on-non-trait.stderr
+++ b/src/test/ui/marker_trait_attr/marker-attribute-on-non-trait.stderr
@@ -1,4 +1,4 @@
-error: attribute can only be applied to a trait
+error: attribute should be applied to a trait
   --> $DIR/marker-attribute-on-non-trait.rs:3:1
    |
 LL | #[marker]
@@ -6,7 +6,7 @@ LL | #[marker]
 LL | struct Struct {}
    | ---------------- not a trait
 
-error: attribute can only be applied to a trait
+error: attribute should be applied to a trait
   --> $DIR/marker-attribute-on-non-trait.rs:6:1
    |
 LL | #[marker]
@@ -14,7 +14,7 @@ LL | #[marker]
 LL | impl Struct {}
    | -------------- not a trait
 
-error: attribute can only be applied to a trait
+error: attribute should be applied to a trait
   --> $DIR/marker-attribute-on-non-trait.rs:9:1
    |
 LL |   #[marker]
@@ -24,7 +24,7 @@ LL | |     x: i32,
 LL | | }
    | |_- not a trait
 
-error: attribute can only be applied to a trait
+error: attribute should be applied to a trait
   --> $DIR/marker-attribute-on-non-trait.rs:14:1
    |
 LL | #[marker]
@@ -32,7 +32,7 @@ LL | #[marker]
 LL | const CONST: usize = 10;
    | ------------------------ not a trait
 
-error: attribute can only be applied to a trait
+error: attribute should be applied to a trait
   --> $DIR/marker-attribute-on-non-trait.rs:17:1
    |
 LL | #[marker]
@@ -40,7 +40,7 @@ LL | #[marker]
 LL | fn function() {}
    | ---------------- not a trait
 
-error: attribute can only be applied to a trait
+error: attribute should be applied to a trait
   --> $DIR/marker-attribute-on-non-trait.rs:20:1
    |
 LL | #[marker]
diff --git a/src/test/ui/rfc-2008-non-exhaustive/invalid-attribute.rs b/src/test/ui/rfc-2008-non-exhaustive/invalid-attribute.rs
index 3c4a09fafd2db..143f9a3009b61 100644
--- a/src/test/ui/rfc-2008-non-exhaustive/invalid-attribute.rs
+++ b/src/test/ui/rfc-2008-non-exhaustive/invalid-attribute.rs
@@ -3,11 +3,11 @@
 struct Foo;
 
 #[non_exhaustive]
-//~^ ERROR attribute can only be applied to a struct or enum [E0701]
+//~^ ERROR attribute should be applied to a struct or enum [E0701]
 trait Bar { }
 
 #[non_exhaustive]
-//~^ ERROR attribute can only be applied to a struct or enum [E0701]
+//~^ ERROR attribute should be applied to a struct or enum [E0701]
 union Baz {
     f1: u16,
     f2: u16
diff --git a/src/test/ui/rfc-2008-non-exhaustive/invalid-attribute.stderr b/src/test/ui/rfc-2008-non-exhaustive/invalid-attribute.stderr
index 76d9e2d8205b7..136cd763b05c1 100644
--- a/src/test/ui/rfc-2008-non-exhaustive/invalid-attribute.stderr
+++ b/src/test/ui/rfc-2008-non-exhaustive/invalid-attribute.stderr
@@ -4,7 +4,7 @@ error: malformed `non_exhaustive` attribute input
 LL | #[non_exhaustive(anything)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[non_exhaustive]`
 
-error[E0701]: attribute can only be applied to a struct or enum
+error[E0701]: attribute should be applied to a struct or enum
   --> $DIR/invalid-attribute.rs:5:1
    |
 LL | #[non_exhaustive]
@@ -13,7 +13,7 @@ LL |
 LL | trait Bar { }
    | ------------- not a struct or enum
 
-error[E0701]: attribute can only be applied to a struct or enum
+error[E0701]: attribute should be applied to a struct or enum
   --> $DIR/invalid-attribute.rs:9:1
    |
 LL |   #[non_exhaustive]
diff --git a/src/test/ui/rfc-2091-track-caller/only-for-fns.rs b/src/test/ui/rfc-2091-track-caller/only-for-fns.rs
index bc0ca9552806f..2d2b01b6f947a 100644
--- a/src/test/ui/rfc-2091-track-caller/only-for-fns.rs
+++ b/src/test/ui/rfc-2091-track-caller/only-for-fns.rs
@@ -1,5 +1,5 @@
 #[track_caller]
 struct S;
-//~^^ ERROR attribute should be applied to function
+//~^^ ERROR attribute should be applied to a function definition
 
 fn main() {}
diff --git a/src/test/ui/rfc-2091-track-caller/only-for-fns.stderr b/src/test/ui/rfc-2091-track-caller/only-for-fns.stderr
index 6666dcfa6e599..b36597bded941 100644
--- a/src/test/ui/rfc-2091-track-caller/only-for-fns.stderr
+++ b/src/test/ui/rfc-2091-track-caller/only-for-fns.stderr
@@ -1,10 +1,10 @@
-error[E0739]: attribute should be applied to function
+error[E0739]: attribute should be applied to a function definition
   --> $DIR/only-for-fns.rs:1:1
    |
 LL | #[track_caller]
    | ^^^^^^^^^^^^^^^
 LL | struct S;
-   | --------- not a function
+   | --------- not a function definition
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/rustdoc/doc_keyword.rs b/src/test/ui/rustdoc/doc_keyword.rs
index 43b84e5018cda..68a8802b2f645 100644
--- a/src/test/ui/rustdoc/doc_keyword.rs
+++ b/src/test/ui/rustdoc/doc_keyword.rs
@@ -15,6 +15,6 @@ fn foo() {}
 // Regression test for the ICE described in #83512.
 trait Foo {
     #[doc(keyword = "match")]
-    //~^ ERROR: `#[doc(keyword = "...")]` can only be used on modules
+    //~^ ERROR: `#[doc(keyword = "...")]` should be used on modules
     fn quux() {}
 }
diff --git a/src/test/ui/rustdoc/doc_keyword.stderr b/src/test/ui/rustdoc/doc_keyword.stderr
index 6ba7034d54122..a1d0e4ffc0938 100644
--- a/src/test/ui/rustdoc/doc_keyword.stderr
+++ b/src/test/ui/rustdoc/doc_keyword.stderr
@@ -1,16 +1,16 @@
-error: `#[doc(keyword = "...")]` can only be used on empty modules
+error: `#[doc(keyword = "...")]` should be used on empty modules
   --> $DIR/doc_keyword.rs:6:7
    |
 LL | #[doc(keyword = "hell")]
    |       ^^^^^^^^^^^^^^^^
 
-error: `#[doc(keyword = "...")]` can only be used on modules
+error: `#[doc(keyword = "...")]` should be used on modules
   --> $DIR/doc_keyword.rs:11:7
    |
 LL | #[doc(keyword = "hall")]
    |       ^^^^^^^^^^^^^^^^
 
-error: `#[doc(keyword = "...")]` can only be used on modules
+error: `#[doc(keyword = "...")]` should be used on modules
   --> $DIR/doc_keyword.rs:17:11
    |
 LL |     #[doc(keyword = "match")]
diff --git a/src/test/ui/span/borrowck-let-suggestion-suffixes.rs b/src/test/ui/span/borrowck-let-suggestion-suffixes.rs
index 4744f3710ce53..6240f103c99b0 100644
--- a/src/test/ui/span/borrowck-let-suggestion-suffixes.rs
+++ b/src/test/ui/span/borrowck-let-suggestion-suffixes.rs
@@ -20,7 +20,7 @@ fn f() {
     //~^ ERROR temporary value dropped while borrowed
     //~| NOTE creates a temporary which is freed while still in use
     //~| NOTE temporary value is freed at the end of this statement
-    //~| NOTE consider using a `let` binding to create a longer lived value
+    //~| HELP consider using a `let` binding to create a longer lived value
 
     {
 
@@ -41,7 +41,7 @@ fn f() {
     //~^ ERROR temporary value dropped while borrowed
     //~| NOTE creates a temporary which is freed while still in use
     //~| NOTE temporary value is freed at the end of this statement
-    //~| NOTE consider using a `let` binding to create a longer lived value
+    //~| HELP consider using a `let` binding to create a longer lived value
 
     v1.push(&old[0]);
 
diff --git a/src/test/ui/span/borrowck-let-suggestion-suffixes.stderr b/src/test/ui/span/borrowck-let-suggestion-suffixes.stderr
index 7c5caba6eae32..a236dab3ae562 100644
--- a/src/test/ui/span/borrowck-let-suggestion-suffixes.stderr
+++ b/src/test/ui/span/borrowck-let-suggestion-suffixes.stderr
@@ -21,7 +21,11 @@ LL |     v3.push(&id('x'));           // statement 6
 LL |     (v1, v2, v3, /* v4 is above. */ v5).use_ref();
    |              -- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = id('x');
+LL ~     v3.push(&binding);           // statement 6
+   |
 
 error[E0716]: temporary value dropped while borrowed
   --> $DIR/borrowck-let-suggestion-suffixes.rs:29:18
@@ -47,7 +51,11 @@ LL |     v5.push(&id('z'));
 LL |     (v1, v2, v3, /* v4 is above. */ v5).use_ref();
    |                                     -- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = id('z');
+LL ~     v5.push(&binding);
+   |
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/span/borrowck-ref-into-rvalue.fixed b/src/test/ui/span/borrowck-ref-into-rvalue.fixed
new file mode 100644
index 0000000000000..51f65e5345d2a
--- /dev/null
+++ b/src/test/ui/span/borrowck-ref-into-rvalue.fixed
@@ -0,0 +1,13 @@
+// run-rustfix
+fn main() {
+    let msg;
+    let binding = Some("Hello".to_string());
+    match binding {
+        //~^ ERROR temporary value dropped while borrowed
+        Some(ref m) => {
+            msg = m;
+        },
+        None => { panic!() }
+    }
+    println!("{}", *msg);
+}
diff --git a/src/test/ui/span/borrowck-ref-into-rvalue.rs b/src/test/ui/span/borrowck-ref-into-rvalue.rs
index c11aa1af54095..7b09fad927fdf 100644
--- a/src/test/ui/span/borrowck-ref-into-rvalue.rs
+++ b/src/test/ui/span/borrowck-ref-into-rvalue.rs
@@ -1,3 +1,4 @@
+// run-rustfix
 fn main() {
     let msg;
     match Some("Hello".to_string()) {
diff --git a/src/test/ui/span/borrowck-ref-into-rvalue.stderr b/src/test/ui/span/borrowck-ref-into-rvalue.stderr
index 4f529ce9511db..cb5289d24b4fc 100644
--- a/src/test/ui/span/borrowck-ref-into-rvalue.stderr
+++ b/src/test/ui/span/borrowck-ref-into-rvalue.stderr
@@ -1,5 +1,5 @@
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/borrowck-ref-into-rvalue.rs:3:11
+  --> $DIR/borrowck-ref-into-rvalue.rs:4:11
    |
 LL |     match Some("Hello".to_string()) {
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^ creates a temporary which is freed while still in use
@@ -9,7 +9,11 @@ LL |     }
 LL |     println!("{}", *msg);
    |                    ---- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = Some("Hello".to_string());
+LL ~     match binding {
+   |
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/span/issue-15480.fixed b/src/test/ui/span/issue-15480.fixed
new file mode 100644
index 0000000000000..e6d1a4dd32806
--- /dev/null
+++ b/src/test/ui/span/issue-15480.fixed
@@ -0,0 +1,14 @@
+// run-rustfix
+fn id<T>(x: T) -> T { x }
+
+fn main() {
+    let binding = id(3);
+    let v = vec![
+        &binding
+    ];
+    //~^^ ERROR temporary value dropped while borrowed
+
+    for &&x in &v {
+        println!("{}", x + 3);
+    }
+}
diff --git a/src/test/ui/span/issue-15480.rs b/src/test/ui/span/issue-15480.rs
index b286d94178a1e..916ce4b1edb26 100644
--- a/src/test/ui/span/issue-15480.rs
+++ b/src/test/ui/span/issue-15480.rs
@@ -1,3 +1,4 @@
+// run-rustfix
 fn id<T>(x: T) -> T { x }
 
 fn main() {
diff --git a/src/test/ui/span/issue-15480.stderr b/src/test/ui/span/issue-15480.stderr
index 23ee2256dd85b..460ad9ac74445 100644
--- a/src/test/ui/span/issue-15480.stderr
+++ b/src/test/ui/span/issue-15480.stderr
@@ -1,5 +1,5 @@
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/issue-15480.rs:5:10
+  --> $DIR/issue-15480.rs:6:10
    |
 LL |         &id(3)
    |          ^^^^^ creates a temporary which is freed while still in use
@@ -9,7 +9,12 @@ LL |     ];
 LL |     for &&x in &v {
    |                -- borrow later used here
    |
-   = note: consider using a `let` binding to create a longer lived value
+help: consider using a `let` binding to create a longer lived value
+   |
+LL ~     let binding = id(3);
+LL ~     let v = vec![
+LL ~         &binding
+   |
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/target-feature/invalid-attribute.stderr b/src/test/ui/target-feature/invalid-attribute.stderr
index 25a2c1975e7b2..889ced9752bd4 100644
--- a/src/test/ui/target-feature/invalid-attribute.stderr
+++ b/src/test/ui/target-feature/invalid-attribute.stderr
@@ -34,43 +34,43 @@ LL | fn bar() {}
    = note: see issue #69098 <https://github.com/rust-lang/rust/issues/69098> for more information
    = help: add `#![feature(target_feature_11)]` to the crate attributes to enable
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/invalid-attribute.rs:34:1
    |
 LL | #[target_feature(enable = "sse2")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
 LL | mod another {}
-   | -------------- not a function
+   | -------------- not a function definition
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/invalid-attribute.rs:39:1
    |
 LL | #[target_feature(enable = "sse2")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
 LL | const FOO: usize = 7;
-   | --------------------- not a function
+   | --------------------- not a function definition
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/invalid-attribute.rs:44:1
    |
 LL | #[target_feature(enable = "sse2")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
 LL | struct Foo;
-   | ----------- not a function
+   | ----------- not a function definition
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/invalid-attribute.rs:49:1
    |
 LL | #[target_feature(enable = "sse2")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
 LL | enum Bar {}
-   | ----------- not a function
+   | ----------- not a function definition
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/invalid-attribute.rs:54:1
    |
 LL |   #[target_feature(enable = "sse2")]
@@ -81,16 +81,16 @@ LL | |
 LL | |     f1: u16,
 LL | |     f2: u16,
 LL | | }
-   | |_- not a function
+   | |_- not a function definition
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/invalid-attribute.rs:62:1
    |
 LL | #[target_feature(enable = "sse2")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
 LL | trait Baz {}
-   | ------------ not a function
+   | ------------ not a function definition
 
 error: cannot use `#[inline(always)]` with `#[target_feature]`
   --> $DIR/invalid-attribute.rs:67:1
@@ -98,7 +98,7 @@ error: cannot use `#[inline(always)]` with `#[target_feature]`
 LL | #[inline(always)]
    | ^^^^^^^^^^^^^^^^^
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/invalid-attribute.rs:85:5
    |
 LL |       #[target_feature(enable = "sse2")]
@@ -108,16 +108,16 @@ LL | /     unsafe {
 LL | |         foo();
 LL | |         bar();
 LL | |     }
-   | |_____- not a function
+   | |_____- not a function definition
 
-error: attribute should be applied to a function
+error: attribute should be applied to a function definition
   --> $DIR/invalid-attribute.rs:93:5
    |
 LL |     #[target_feature(enable = "sse2")]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
 LL |     || {};
-   |     ----- not a function
+   |     ----- not a function definition
 
 error[E0658]: `#[target_feature(..)]` can only be applied to `unsafe` functions
   --> $DIR/invalid-attribute.rs:77:5
diff --git a/src/test/ui/traits/default-method/rustc_must_implement_one_of_misuse.rs b/src/test/ui/traits/default-method/rustc_must_implement_one_of_misuse.rs
index d9de6d5edb9b4..1f896da94db57 100644
--- a/src/test/ui/traits/default-method/rustc_must_implement_one_of_misuse.rs
+++ b/src/test/ui/traits/default-method/rustc_must_implement_one_of_misuse.rs
@@ -36,11 +36,11 @@ trait Tr5 {
 }
 
 #[rustc_must_implement_one_of(abc, xyz)]
-//~^ attribute can only be applied to a trait
+//~^ attribute should be applied to a trait
 fn function() {}
 
 #[rustc_must_implement_one_of(abc, xyz)]
-//~^ attribute can only be applied to a trait
+//~^ attribute should be applied to a trait
 struct Struct {}
 
 fn main() {}
diff --git a/src/test/ui/traits/default-method/rustc_must_implement_one_of_misuse.stderr b/src/test/ui/traits/default-method/rustc_must_implement_one_of_misuse.stderr
index bc28dc2c4f40d..869184f0d1a69 100644
--- a/src/test/ui/traits/default-method/rustc_must_implement_one_of_misuse.stderr
+++ b/src/test/ui/traits/default-method/rustc_must_implement_one_of_misuse.stderr
@@ -4,7 +4,7 @@ error: malformed `rustc_must_implement_one_of` attribute input
 LL | #[rustc_must_implement_one_of]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[rustc_must_implement_one_of(function1, function2, ...)]`
 
-error: attribute can only be applied to a trait
+error: attribute should be applied to a trait
   --> $DIR/rustc_must_implement_one_of_misuse.rs:38:1
    |
 LL | #[rustc_must_implement_one_of(abc, xyz)]
@@ -13,7 +13,7 @@ LL |
 LL | fn function() {}
    | ---------------- not a trait
 
-error: attribute can only be applied to a trait
+error: attribute should be applied to a trait
   --> $DIR/rustc_must_implement_one_of_misuse.rs:42:1
    |
 LL | #[rustc_must_implement_one_of(abc, xyz)]
diff --git a/src/test/ui/traits/issue-85735.stderr b/src/test/ui/traits/issue-85735.stderr
index 9e80497ca6e92..fa280135beb2d 100644
--- a/src/test/ui/traits/issue-85735.stderr
+++ b/src/test/ui/traits/issue-85735.stderr
@@ -4,14 +4,7 @@ error[E0283]: type annotations needed: cannot satisfy `T: FnMut<(&'a (),)>`
 LL |     T: FnMut(&'a ()),
    |        ^^^^^^^^^^^^^
    |
-note: multiple `impl`s or `where` clauses satisfying `T: FnMut<(&'a (),)>` found
-  --> $DIR/issue-85735.rs:7:8
-   |
-LL |     T: FnMut(&'a ()),
-   |        ^^^^^^^^^^^^^
-LL |
-LL |     T: FnMut(&'b ()),
-   |        ^^^^^^^^^^^^^
+   = note: cannot satisfy `T: FnMut<(&'a (),)>`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug.rs b/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug.rs
index 811832848d9dd..9a50c0f988a56 100644
--- a/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug.rs
+++ b/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug.rs
@@ -1,8 +1,9 @@
 // compile-flags: --edition=2021
+// check-pass
 #![feature(type_alias_impl_trait)]
 
 fn main() {
-    type T = impl Copy; //~ ERROR unconstrained opaque type
+    type T = impl Copy;
     let foo: T = (1u32, 2u32);
     let (a, b): (u32, u32) = foo;
 }
diff --git a/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug.stderr b/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug.stderr
deleted file mode 100644
index 03b172e6de570..0000000000000
--- a/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-error: unconstrained opaque type
-  --> $DIR/cross_inference_pattern_bug.rs:5:14
-   |
-LL |     type T = impl Copy;
-   |              ^^^^^^^^^
-   |
-   = note: `T` must be used in combination with a concrete type within the same module
-
-error: aborting due to previous error
-
diff --git a/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug_no_type.rs b/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug_no_type.rs
index 328096d44b4b5..b929122a6c23f 100644
--- a/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug_no_type.rs
+++ b/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug_no_type.rs
@@ -1,13 +1,13 @@
-// known-bug: #96572
 // compile-flags: --edition=2021 --crate-type=lib
 // rustc-env:RUST_BACKTRACE=0
+// check-pass
 
 // tracked in https://github.com/rust-lang/rust/issues/96572
 
 #![feature(type_alias_impl_trait)]
 
 fn main() {
-    type T = impl Copy;  // error: unconstrained opaque type
+    type T = impl Copy;
     let foo: T = (1u32, 2u32);
-    let (a, b) = foo; // removing this line makes the code compile
+    let (a, b) = foo; // this line used to make the code fail
 }
diff --git a/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug_no_type.stderr b/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug_no_type.stderr
deleted file mode 100644
index 8aa1f49563995..0000000000000
--- a/src/test/ui/type-alias-impl-trait/cross_inference_pattern_bug_no_type.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-error: unconstrained opaque type
-  --> $DIR/cross_inference_pattern_bug_no_type.rs:10:14
-   |
-LL |     type T = impl Copy;  // error: unconstrained opaque type
-   |              ^^^^^^^^^
-   |
-   = note: `T` must be used in combination with a concrete type within the same module
-
-error: aborting due to previous error
-
diff --git a/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-mismatch.rs b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-mismatch.rs
new file mode 100644
index 0000000000000..825710851b01f
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-mismatch.rs
@@ -0,0 +1,10 @@
+#![feature(type_alias_impl_trait)]
+
+fn main() {
+    type T = impl Copy;
+    let foo: T = Some((1u32, 2u32));
+    match foo {
+        None => (),
+        Some((a, b, c)) => (), //~ ERROR mismatched types
+    }
+}
diff --git a/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-mismatch.stderr b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-mismatch.stderr
new file mode 100644
index 0000000000000..728244a1844db
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-mismatch.stderr
@@ -0,0 +1,15 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-96572-unconstrained-mismatch.rs:8:14
+   |
+LL |     match foo {
+   |           --- this expression has type `T`
+LL |         None => (),
+LL |         Some((a, b, c)) => (),
+   |              ^^^^^^^^^ expected a tuple with 2 elements, found one with 3 elements
+   |
+   = note: expected tuple `(u32, u32)`
+              found tuple `(_, _, _)`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-only-pattern-rpit.rs b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-only-pattern-rpit.rs
new file mode 100644
index 0000000000000..c0a371eca1c6f
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-only-pattern-rpit.rs
@@ -0,0 +1,29 @@
+// check-pass
+
+#[allow(unconditional_recursion)]
+fn foo(b: bool) -> impl Copy {
+    let (mut x, mut y) = foo(false);
+    x = 42;
+    y = "foo";
+    if b {
+        panic!()
+    } else {
+        foo(true)
+    }
+}
+
+fn bar(b: bool) -> Option<impl Copy> {
+    if b {
+        return None;
+    }
+    match bar(!b) {
+        Some((mut x, mut y)) => {
+            x = 42;
+            y = "foo";
+        }
+        None => {}
+    }
+    None
+}
+
+fn main() {}
diff --git a/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-only-pattern.rs b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-only-pattern.rs
new file mode 100644
index 0000000000000..ec249958590f1
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-only-pattern.rs
@@ -0,0 +1,24 @@
+#![feature(type_alias_impl_trait)]
+// check-pass
+
+type T = impl Copy;
+
+fn foo(foo: T) {
+    let (mut x, mut y) = foo;
+    x = 42;
+    y = "foo";
+}
+
+type U = impl Copy;
+
+fn bar(bar: Option<U>) {
+    match bar {
+        Some((mut x, mut y)) => {
+            x = 42;
+            y = "foo";
+        }
+        None => {}
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-struct.rs b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-struct.rs
new file mode 100644
index 0000000000000..3351d9bcff1f8
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-struct.rs
@@ -0,0 +1,11 @@
+#![feature(type_alias_impl_trait)]
+// check-pass
+
+#[derive(Copy, Clone)]
+struct Foo((u32, u32));
+
+fn main() {
+    type U = impl Copy;
+    let foo: U = Foo((1u32, 2u32));
+    let Foo((a, b)) = foo;
+}
diff --git a/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-upvar-enum.rs b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-upvar-enum.rs
new file mode 100644
index 0000000000000..ef3279a98d199
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-upvar-enum.rs
@@ -0,0 +1,13 @@
+#![feature(type_alias_impl_trait)]
+// check-pass
+
+fn main() {
+    type T = impl Copy;
+    let foo: T = Some((1u32, 2u32));
+    let x = move || {
+        match foo {
+            None => (),
+            Some((a, b)) => (),
+        }
+    };
+}
diff --git a/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-upvar.rs b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-upvar.rs
new file mode 100644
index 0000000000000..bb0fc7c7534f5
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained-upvar.rs
@@ -0,0 +1,13 @@
+#![feature(type_alias_impl_trait)]
+// check-pass
+
+#[derive(Copy, Clone)]
+struct Foo((u32, u32));
+
+fn main() {
+    type T = impl Copy;
+    let foo: T = Foo((1u32, 2u32));
+    let x = move || {
+        let Foo((a, b)) = foo;
+    };
+}
diff --git a/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained.rs b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained.rs
new file mode 100644
index 0000000000000..4b9ed7f28eb3f
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/issue-96572-unconstrained.rs
@@ -0,0 +1,11 @@
+#![feature(type_alias_impl_trait)]
+// check-pass
+
+fn main() {
+    type T = impl Copy;
+    let foo: T = Some((1u32, 2u32));
+    match foo {
+        None => (),
+        Some((a, b)) => (),
+    }
+}
diff --git a/src/test/ui/type/type-check/issue-40294.stderr b/src/test/ui/type/type-check/issue-40294.stderr
index d15fd23418bb0..75feb5698eb63 100644
--- a/src/test/ui/type/type-check/issue-40294.stderr
+++ b/src/test/ui/type/type-check/issue-40294.stderr
@@ -4,13 +4,7 @@ error[E0283]: type annotations needed: cannot satisfy `&'a T: Foo`
 LL |     where &'a T : Foo,
    |                   ^^^
    |
-note: multiple `impl`s or `where` clauses satisfying `&'a T: Foo` found
-  --> $DIR/issue-40294.rs:6:19
-   |
-LL |     where &'a T : Foo,
-   |                   ^^^
-LL |           &'b T : Foo
-   |                   ^^^
+   = note: cannot satisfy `&'a T: Foo`
 
 error: aborting due to previous error
 
diff --git a/src/tools/clippy/clippy_lints/src/format.rs b/src/tools/clippy/clippy_lints/src/format.rs
index 3084c70589fa3..0aa085fc71bfe 100644
--- a/src/tools/clippy/clippy_lints/src/format.rs
+++ b/src/tools/clippy/clippy_lints/src/format.rs
@@ -82,7 +82,7 @@ impl<'tcx> LateLintPass<'tcx> for UselessFormat {
                 then {
                     let is_new_string = match value.kind {
                         ExprKind::Binary(..) => true,
-                        ExprKind::MethodCall(path, ..) => path.ident.name.as_str() == "to_string",
+                        ExprKind::MethodCall(path, ..) => path.ident.name == sym::to_string,
                         _ => false,
                     };
                     let sugg = if format_args.format_string_span.contains(value.span) {
diff --git a/src/tools/clippy/clippy_lints/src/inherent_to_string.rs b/src/tools/clippy/clippy_lints/src/inherent_to_string.rs
index 94db1773fda69..17d867aacb533 100644
--- a/src/tools/clippy/clippy_lints/src/inherent_to_string.rs
+++ b/src/tools/clippy/clippy_lints/src/inherent_to_string.rs
@@ -98,7 +98,7 @@ impl<'tcx> LateLintPass<'tcx> for InherentToString {
         if_chain! {
             // Check if item is a method, called to_string and has a parameter 'self'
             if let ImplItemKind::Fn(ref signature, _) = impl_item.kind;
-            if impl_item.ident.name.as_str() == "to_string";
+            if impl_item.ident.name == sym::to_string;
             let decl = &signature.decl;
             if decl.implicit_self.has_implicit_self();
             if decl.inputs.len() == 1;
diff --git a/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs b/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs
index b4c6bfb31ed1c..b3276f1394ed2 100644
--- a/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs
@@ -427,5 +427,5 @@ fn is_cow_into_owned(cx: &LateContext<'_>, method_name: Symbol, method_def_id: D
 
 /// Returns true if the named method is `ToString::to_string`.
 fn is_to_string(cx: &LateContext<'_>, method_name: Symbol, method_def_id: DefId) -> bool {
-    method_name.as_str() == "to_string" && is_diag_trait_item(cx, method_def_id, sym::ToString)
+    method_name == sym::to_string && is_diag_trait_item(cx, method_def_id, sym::ToString)
 }
diff --git a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
index 3bf75bcbee83e..9690ad2777177 100644
--- a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
+++ b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
@@ -252,6 +252,7 @@ fn check_place<'tcx>(tcx: TyCtxt<'tcx>, place: Place<'tcx>, span: Span, body: &B
                 }
             },
             ProjectionElem::ConstantIndex { .. }
+            | ProjectionElem::OpaqueCast(..)
             | ProjectionElem::Downcast(..)
             | ProjectionElem::Subslice { .. }
             | ProjectionElem::Deref