Fix some loop block coercion diagnostics

compiler/rustc_hir_typeck/src/coercion.rs

@@ -54,7 +54,7 @@ use rustc_middle::ty::adjustment::{
 };
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
-use rustc_span::{BytePos, DUMMY_SP, DesugaringKind, Span};
+use rustc_span::{BytePos, DUMMY_SP, Span};
 use rustc_trait_selection::infer::InferCtxtExt as _;
 use rustc_trait_selection::solve::inspect::{self, InferCtxtProofTreeExt, ProofTreeVisitor};
 use rustc_trait_selection::solve::{Certainty, Goal, NoSolution};
@@ -1828,10 +1828,9 @@ impl<'tcx> CoerceMany<'tcx> {
                 // If the block is from an external macro or try (`?`) desugaring, then
                 // do not suggest adding a semicolon, because there's nowhere to put it.
                 // See issues #81943 and #87051.
-                && matches!(
-                    cond_expr.span.desugaring_kind(),
-                    None | Some(DesugaringKind::WhileLoop)
-                )
+                // Similarly, if the block is from a loop desugaring, then also do not
+                // suggest adding a semicolon. See issue #150850.
+                && cond_expr.span.desugaring_kind().is_none()
                 && !cond_expr.span.in_external_macro(fcx.tcx.sess.source_map())
                 && !matches!(
                     cond_expr.kind,

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -10,8 +10,8 @@ use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{
     self as hir, Arm, CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, ExprKind,
-    GenericBound, HirId, Node, PatExpr, PatExprKind, Path, QPath, Stmt, StmtKind, TyKind,
-    WherePredicateKind, expr_needs_parens, is_range_literal,
+    GenericBound, HirId, LoopSource, Node, PatExpr, PatExprKind, Path, QPath, Stmt, StmtKind,
+    TyKind, WherePredicateKind, expr_needs_parens, is_range_literal,
 };
 use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer;
 use rustc_hir_analysis::suggest_impl_trait;
@@ -1170,23 +1170,31 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
         let found = self.resolve_vars_if_possible(found);
 
-        let in_loop = self.is_loop(id)
-            || self
-                .tcx
+        let innermost_loop = if self.is_loop(id) {
+            Some(self.tcx.hir_node(id))
+        } else {
+            self.tcx
                 .hir_parent_iter(id)
                 .take_while(|(_, node)| {
                     // look at parents until we find the first body owner
                     node.body_id().is_none()
                 })
-                .any(|(parent_id, _)| self.is_loop(parent_id));
+                .find_map(|(parent_id, node)| self.is_loop(parent_id).then_some(node))
+        };
+        let can_break_with_value = innermost_loop.is_some_and(|node| {
+            matches!(
+                node,
+                Node::Expr(Expr { kind: ExprKind::Loop(_, _, LoopSource::Loop, ..), .. })
+            )
+        });
 
         let in_local_statement = self.is_local_statement(id)
             || self
                 .tcx
                 .hir_parent_iter(id)
                 .any(|(parent_id, _)| self.is_local_statement(parent_id));
 
-        if in_loop && in_local_statement {
+        if can_break_with_value && in_local_statement {
             err.multipart_suggestion(
                 "you might have meant to break the loop with this value",
                 vec![

tests/ui/block-result/block-must-not-have-result-while.stderr

@@ -9,12 +9,8 @@ LL |     while true {
 error[E0308]: mismatched types
   --> $DIR/block-must-not-have-result-while.rs:5:9
    |
-LL | /     while true {
-LL | |         true
-   | |         ^^^^ expected `()`, found `bool`
-LL | |
-LL | |     }
-   | |_____- expected this to be `()`
+LL |         true
+   |         ^^^^ expected `()`, found `bool`
 
 error: aborting due to 1 previous error; 1 warning emitted
 

tests/ui/for-loop-while/dont-suggest-break-from-unbreakable-loops.rs

@@ -0,0 +1,39 @@
+//! Don't suggest breaking with value from `for` or `while` loops
+//!
+//! Regression test for https://github.com/rust-lang/rust/issues/150850
+
+fn returns_i32() -> i32 { 0 }
+
+fn suggest_breaking_from_loop() {
+    let _ = loop {
+        returns_i32() //~ ERROR mismatched types
+        //~^ SUGGESTION ;
+        //~| SUGGESTION break
+    };
+}
+
+fn dont_suggest_breaking_from_for() {
+    let _ = for _ in 0.. {
+        returns_i32() //~ ERROR mismatched types
+        //~^ SUGGESTION ;
+    };
+}
+
+fn dont_suggest_breaking_from_while() {
+    let cond = true;
+    let _ = while cond {
+        returns_i32() //~ ERROR mismatched types
+        //~^ SUGGESTION ;
+    };
+}
+
+fn dont_suggest_breaking_from_for_nested_in_loop() {
+    let _ = loop {
+        for _ in 0.. {
+            returns_i32() //~ ERROR mismatched types
+            //~^ SUGGESTION ;
+        }
+    };
+}
+
+fn main() {}

tests/ui/for-loop-while/dont-suggest-break-from-unbreakable-loops.stderr

@@ -0,0 +1,42 @@
+error[E0308]: mismatched types
+  --> $DIR/dont-suggest-break-from-unbreakable-loops.rs:9:9
+   |
+LL |         returns_i32()
+   |         ^^^^^^^^^^^^^ expected `()`, found `i32`
+   |
+help: consider using a semicolon here
+   |
+LL |         returns_i32();
+   |                      +
+help: you might have meant to break the loop with this value
+   |
+LL |         break returns_i32();
+   |         +++++              +
+
+error[E0308]: mismatched types
+  --> $DIR/dont-suggest-break-from-unbreakable-loops.rs:17:9
+   |
+LL |         returns_i32()
+   |         ^^^^^^^^^^^^^- help: consider using a semicolon here: `;`
+   |         |
+   |         expected `()`, found `i32`
+
+error[E0308]: mismatched types
+  --> $DIR/dont-suggest-break-from-unbreakable-loops.rs:25:9
+   |
+LL |         returns_i32()
+   |         ^^^^^^^^^^^^^- help: consider using a semicolon here: `;`
+   |         |
+   |         expected `()`, found `i32`
+
+error[E0308]: mismatched types
+  --> $DIR/dont-suggest-break-from-unbreakable-loops.rs:33:13
+   |
+LL |             returns_i32()
+   |             ^^^^^^^^^^^^^- help: consider using a semicolon here: `;`
+   |             |
+   |             expected `()`, found `i32`
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0308`.