From a78e87329dbe66ad6cdfdb0d41e0abc18a0076ed Mon Sep 17 00:00:00 2001
From: Albab-Hasan <albabhasan276@gmail.com>
Date: Sat, 14 Feb 2026 22:19:26 +0600
Subject: [PATCH] fix: handle `ref mut` bindings in
 `contains_explicit_ref_binding`

the standalone `contains_explicit_ref_binding` function only checked for
`BindingAnnotation::Ref`, missing `BindingAnnotation::RefMut`. this caused
`let ref mut x = expr` to incorrectly take the coercion path instead of
preserving the exact type of the rhs expression. the method version used
for match arms already handles both `Ref` and `RefMut` correctly.
---
 crates/hir-ty/src/infer/pat.rs        |  2 +-
 crates/hir-ty/src/tests/never_type.rs | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/crates/hir-ty/src/infer/pat.rs b/crates/hir-ty/src/infer/pat.rs
index 1b8ce5ceaf86..87fd0dace38f 100644
--- a/crates/hir-ty/src/infer/pat.rs
+++ b/crates/hir-ty/src/infer/pat.rs
@@ -673,7 +673,7 @@ impl<'db> InferenceContext<'_, 'db> {
 pub(super) fn contains_explicit_ref_binding(body: &Body, pat_id: PatId) -> bool {
     let mut res = false;
     body.walk_pats(pat_id, &mut |pat| {
-        res |= matches!(body[pat], Pat::Bind { id, .. } if body[id].mode == BindingAnnotation::Ref);
+        res |= matches!(body[pat], Pat::Bind { id, .. } if matches!(body[id].mode, BindingAnnotation::Ref | BindingAnnotation::RefMut));
     });
     res
 }
diff --git a/crates/hir-ty/src/tests/never_type.rs b/crates/hir-ty/src/tests/never_type.rs
index 4d68179a88b8..a89d97984dfe 100644
--- a/crates/hir-ty/src/tests/never_type.rs
+++ b/crates/hir-ty/src/tests/never_type.rs
@@ -760,6 +760,32 @@ fn coerce_ref_binding() -> ! {
     )
 }
 
+#[test]
+fn diverging_place_match_ref_mut() {
+    check_infer_with_mismatches(
+        r#"
+//- minicore: sized
+fn coerce_ref_mut_binding() -> ! {
+    unsafe {
+        let x: *mut ! = 0 as _;
+        let ref mut _x: () = *x;
+    }
+}
+"#,
+        expect![[r#"
+            33..120 '{     ...   } }': !
+            39..118 'unsafe...     }': !
+            60..61 'x': *mut !
+            72..73 '0': i32
+            72..78 '0 as _': *mut !
+            92..102 'ref mut _x': &'? mut ()
+            109..111 '*x': !
+            110..111 'x': *mut !
+            109..111: expected (), got !
+        "#]],
+    )
+}
+
 #[test]
 fn never_place_isnt_diverging() {
     check_infer_with_mismatches(