Make "remove semicolon" suggestion work with !

compiler/rustc_infer/src/infer/error_reporting/suggest.rs

@@ -714,6 +714,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         let last_expr_ty = self.typeck_results.as_ref()?.expr_ty_opt(last_expr)?;
         let needs_box = match (last_expr_ty.kind(), expected_ty.kind()) {
             _ if last_expr_ty.references_error() => return None,
+            (ty::Never, _) => StatementAsExpression::CorrectType,
             _ if self.same_type_modulo_infer(last_expr_ty, expected_ty) => {
                 StatementAsExpression::CorrectType
             }

tests/ui/editions/diverging-block.e2024.fixed

@@ -0,0 +1,31 @@
+//@ revisions: e2021 e2024
+//
+//@[e2021] edition: 2021
+//@[e2024] edition: 2024
+//@[e2024] compile-flags: -Zunstable-options
+//
+//@[e2021] check-pass
+//@[e2024] check-fail
+//
+//@[e2024] run-rustfix
+#![crate_name = "diverging_block"] // or else rustfix dies because of dots in the crate name
+
+
+fn main() {
+    // a diverging block, with no tail expression.
+    //
+    // edition <= 2021: the block has type `!`, which then can be coerced.
+    // edition >= 2024: the block has type `()`, as with any block with no tail.
+    let _: u32 = { //[e2024]~ error: mismatched types
+        return
+    };
+}
+
+fn _f() {
+    // Same as the above, but with an if
+    if true {
+        return
+    } else {
+        0_u32 //[e2024]~ error: `if` and `else` have incompatible types
+    };
+}

tests/ui/editions/diverging-block.e2024.stderr

@@ -1,18 +1,22 @@
 error[E0308]: mismatched types
-  --> $DIR/diverging-block.rs:15:18
+  --> $DIR/diverging-block.rs:19:18
    |
 LL |       let _: u32 = {
    |  __________________^
 LL | |         return;
+   | |               - help: remove this semicolon to return this value
 LL | |     };
    | |_____^ expected `u32`, found `()`
 
 error[E0308]: `if` and `else` have incompatible types
-  --> $DIR/diverging-block.rs:25:9
+  --> $DIR/diverging-block.rs:29:9
    |
 LL | /     if true {
 LL | |         return;
-   | |         ------- expected because of this
+   | |         -------
+   | |         |     |
+   | |         |     help: consider removing this semicolon
+   | |         expected because of this
 LL | |     } else {
 LL | |         0_u32
    | |         ^^^^^ expected `()`, found `u32`

tests/ui/editions/diverging-block.rs

@@ -6,6 +6,10 @@
 //
 //@[e2021] check-pass
 //@[e2024] check-fail
+//
+//@[e2024] run-rustfix
+#![crate_name = "diverging_block"] // or else rustfix dies because of dots in the crate name
+
 
 fn main() {
     // a diverging block, with no tail expression.