From 5e00484c38c2ce8084f081678afe47474dbe85ad Mon Sep 17 00:00:00 2001
From: yukang <moorekang@gmail.com>
Date: Sat, 25 Apr 2026 16:27:05 +0800
Subject: [PATCH] Avoid misleading closure return type note

---
 compiler/rustc_hir_typeck/src/coercion.rs          |  3 +++
 .../closure-return-block-note-issue-155670.rs      | 14 ++++++++++++++
 .../closure-return-block-note-issue-155670.stderr  |  9 +++++++++
 3 files changed, 26 insertions(+)
 create mode 100644 tests/ui/closures/closure-return-block-note-issue-155670.rs
 create mode 100644 tests/ui/closures/closure-return-block-note-issue-155670.stderr

diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index e34628bad66b4..4dac314b91812 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -2009,6 +2009,9 @@ impl<'tcx> CoerceMany<'tcx> {
             // 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"));
         }
diff --git a/tests/ui/closures/closure-return-block-note-issue-155670.rs b/tests/ui/closures/closure-return-block-note-issue-155670.rs
new file mode 100644
index 0000000000000..fccce9ee54ca2
--- /dev/null
+++ b/tests/ui/closures/closure-return-block-note-issue-155670.rs
@@ -0,0 +1,14 @@
+struct SmolStr;
+
+const _: fn() = || {
+    match Some(()) {
+        Some(()) => (),
+        None => return,
+    };
+    let _: String = {
+        SmolStr
+        //~^ ERROR mismatched types
+    };
+};
+
+fn main() {}
diff --git a/tests/ui/closures/closure-return-block-note-issue-155670.stderr b/tests/ui/closures/closure-return-block-note-issue-155670.stderr
new file mode 100644
index 0000000000000..f38d2f14200d4
--- /dev/null
+++ b/tests/ui/closures/closure-return-block-note-issue-155670.stderr
@@ -0,0 +1,9 @@
+error[E0308]: mismatched types
+  --> $DIR/closure-return-block-note-issue-155670.rs:9:9
+   |
+LL |         SmolStr
+   |         ^^^^^^^ expected `String`, found `SmolStr`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.