From df6254f7a204b383bd8346880247a68dc32cab32 Mon Sep 17 00:00:00 2001
From: Jonathan Gruner <jogru0@gmail.com>
Date: Tue, 8 Apr 2025 20:49:50 +0200
Subject: [PATCH 1/2] report call site of inlined scopes for large assignment
 lints

---
 .../src/mono_checks/move_check.rs             | 20 +++++++++++++---
 tests/ui/lint/large_assignments/inline_mir.rs | 24 +++++++++++++++++++
 .../lint/large_assignments/inline_mir.stderr  | 15 ++++++++++++
 3 files changed, 56 insertions(+), 3 deletions(-)
 create mode 100644 tests/ui/lint/large_assignments/inline_mir.rs
 create mode 100644 tests/ui/lint/large_assignments/inline_mir.stderr

diff --git a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
index 838bfdab1ea59..946714e3e48a1 100644
--- a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
+++ b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
@@ -162,13 +162,27 @@ impl<'tcx> MoveCheckVisitor<'tcx> {
             // but correct span? This would make the lint at least accept crate-level lint attributes.
             return;
         };
+
+        // If the source scope is inlined by the MIR inliner, report the lint on the call site.
+        let reported_span = self
+            .body
+            .source_scopes
+            .get(source_info.scope)
+            .and_then(|source_scope_data| source_scope_data.inlined)
+            .map(|(_, call_site)| call_site)
+            .unwrap_or(span);
+
         self.tcx.emit_node_span_lint(
             LARGE_ASSIGNMENTS,
             lint_root,
-            span,
-            LargeAssignmentsLint { span, size: too_large_size.bytes(), limit: limit as u64 },
+            reported_span,
+            LargeAssignmentsLint {
+                span: reported_span,
+                size: too_large_size.bytes(),
+                limit: limit as u64,
+            },
         );
-        self.move_size_spans.push(span);
+        self.move_size_spans.push(reported_span);
     }
 }
 
diff --git a/tests/ui/lint/large_assignments/inline_mir.rs b/tests/ui/lint/large_assignments/inline_mir.rs
new file mode 100644
index 0000000000000..fc27b8ff244d1
--- /dev/null
+++ b/tests/ui/lint/large_assignments/inline_mir.rs
@@ -0,0 +1,24 @@
+#![feature(large_assignments)]
+#![deny(large_assignments)]
+#![move_size_limit = "1000"]
+
+//! Tests that with `-Zinline-mir`, we do NOT get an error that points to the
+//! implementation of `UnsafeCell` since that is not actionable by the user:
+//!
+//! ```text
+//! error: moving 9999 bytes
+//!   --> /rustc/FAKE_PREFIX/library/core/src/cell.rs:2054:9
+//!    |
+//!    = note: value moved from here
+//! ```
+//!
+//! We want the diagnostics to point to the relevant user code.
+
+//@ build-fail
+//@ compile-flags: -Zmir-opt-level=1 -Zinline-mir
+
+pub fn main() {
+    let data = [10u8; 9999];
+    let cell = std::cell::UnsafeCell::new(data); //~ ERROR large_assignments
+    std::hint::black_box(cell);
+}
diff --git a/tests/ui/lint/large_assignments/inline_mir.stderr b/tests/ui/lint/large_assignments/inline_mir.stderr
new file mode 100644
index 0000000000000..d9010e24d03be
--- /dev/null
+++ b/tests/ui/lint/large_assignments/inline_mir.stderr
@@ -0,0 +1,15 @@
+error: moving 9999 bytes
+  --> $DIR/inline_mir.rs:22:16
+   |
+LL |     let cell = std::cell::UnsafeCell::new(data);
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ value moved from here
+   |
+   = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+note: the lint level is defined here
+  --> $DIR/inline_mir.rs:2:9
+   |
+LL | #![deny(large_assignments)]
+   |         ^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

From 6d71fc15d8983960745bf2f61ab74ca272f0585f Mon Sep 17 00:00:00 2001
From: Jonathan Gruner <jogru0@gmail.com>
Date: Tue, 8 Apr 2025 21:22:20 +0200
Subject: [PATCH 2/2] for large assignment lint, use the correct span for
 checking for duplicate lints

---
 .../src/mono_checks/move_check.rs                   | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
index 946714e3e48a1..a484573f0d860 100644
--- a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
+++ b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
@@ -148,11 +148,7 @@ impl<'tcx> MoveCheckVisitor<'tcx> {
         span: Span,
     ) {
         let source_info = self.body.source_info(location);
-        for reported_span in &self.move_size_spans {
-            if reported_span.overlaps(span) {
-                return;
-            }
-        }
+
         let lint_root = source_info.scope.lint_root(&self.body.source_scopes);
         let Some(lint_root) = lint_root else {
             // This happens when the issue is in a function from a foreign crate that
@@ -172,6 +168,12 @@ impl<'tcx> MoveCheckVisitor<'tcx> {
             .map(|(_, call_site)| call_site)
             .unwrap_or(span);
 
+        for previously_reported_span in &self.move_size_spans {
+            if previously_reported_span.overlaps(reported_span) {
+                return;
+            }
+        }
+
         self.tcx.emit_node_span_lint(
             LARGE_ASSIGNMENTS,
             lint_root,
@@ -182,6 +184,7 @@ impl<'tcx> MoveCheckVisitor<'tcx> {
                 limit: limit as u64,
             },
         );
+
         self.move_size_spans.push(reported_span);
     }
 }