Avoid misleading closure return type note

compiler/rustc_hir_typeck/src/coercion.rs

@@ -1998,9 +1998,13 @@ fn report_return_mismatched_types<'infcx>(
             );
         }
 
-        let ret_coercion_span = fcx.ret_coercion_span.get();
+        let is_return_position = fcx
+            .tcx
+            .hir_get_fn_id_for_return_block(block_or_return_id)
+            .is_some_and(|fn_id| fn_id == fcx.tcx.local_def_id_to_hir_id(fcx.body_id));
 
-        if let Some(sp) = ret_coercion_span
+        if is_return_position
+            && let Some(sp) = fcx.ret_coercion_span.get()
             // If the closure has an explicit return type annotation, or if
             // the closure's return type has been inferred from outside
             // requirements (such as an Fn* trait bound), then a type error
@@ -2009,9 +2013,6 @@ fn report_return_mismatched_types<'infcx>(
             // note in this case, since it would be incorrect.
             && let Some(fn_sig) = fcx.body_fn_sig()
             && fn_sig.output().is_ty_var()
-            && fcx.ret_coercion.as_ref().is_some_and(|ret_coercion| {
-                fcx.resolve_vars_if_possible(ret_coercion.borrow().expected_ty()) == expected
-            })
         {
             err.span_note(sp, format!("return type inferred to be `{expected}` here"));
         }

tests/ui/closures/closure-return-block-note-issue-155670.rs

@@ -11,4 +11,28 @@
     };
 };
 
+const _: fn() -> SmolStr = || {
+    match Some(()) {
+        Some(()) => (),
+        None => return SmolStr,
+    };
+    let _: String = {
+        SmolStr
+        //~^ ERROR mismatched types
+    };
+    SmolStr
+};
+
+const _: fn() -> String = || {
+    match Some(()) {
+        Some(()) => (),
+        None => return String::new(),
+    };
+    let _: String = {
+        SmolStr
+        //~^ ERROR mismatched types
+    };
+    String::new()
+};
+
 fn main() {}

tests/ui/closures/closure-return-block-note-issue-155670.stderr

@@ -4,6 +4,18 @@ error[E0308]: mismatched types
 LL |         SmolStr
    |         ^^^^^^^ expected `String`, found `SmolStr`
 
-error: aborting due to 1 previous error
+error[E0308]: mismatched types
+  --> $DIR/closure-return-block-note-issue-155670.rs:20:9
+   |
+LL |         SmolStr
+   |         ^^^^^^^ expected `String`, found `SmolStr`
+
+error[E0308]: mismatched types
+  --> $DIR/closure-return-block-note-issue-155670.rs:32:9
+   |
+LL |         SmolStr
+   |         ^^^^^^^ expected `String`, found `SmolStr`
+
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0308`.