[clang] [clang]: fix overload resolution in case of converting const value reference to an rvalue reference. (PR #133035)

[Nhat Nguyen via cfe-commits]

https://github.com/changkhothuychung updated https://github.com/llvm/llvm-project/pull/133035

>From fb9260dd796ae687a000beb550198d155b772625 Mon Sep 17 00:00:00 2001
From: changkhothuychung <nhat7203 at gmail.com>
Date: Wed, 26 Mar 2025 00:55:26 -0400
Subject: [PATCH 1/2] initial commit

---
 clang/lib/Sema/SemaOverload.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 6d8006b35dcf4..28843f378c686 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -5419,7 +5419,7 @@ TryReferenceInit(Sema &S, Expr *Init, QualType DeclType,
   //   the argument expression. Any difference in top-level
   //   cv-qualification is subsumed by the initialization itself
   //   and does not constitute a conversion.
-  ICS = TryImplicitConversion(S, Init, T1, SuppressUserConversions,
+  ICS = TryImplicitConversion(S, Init, DeclType, SuppressUserConversions,
                               AllowedExplicit::None,
                               /*InOverloadResolution=*/false,
                               /*CStyle=*/false,

>From 693049e2bdfe31c1243c9d9a5a7bf59363a2b9b1 Mon Sep 17 00:00:00 2001
From: changkhothuychung <nhat7203 at gmail.com>
Date: Wed, 26 Mar 2025 01:59:45 -0400
Subject: [PATCH 2/2] bound rref to const lref

---
 clang/lib/Sema/SemaOverload.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 28843f378c686..0f4bb69f713f8 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -5419,7 +5419,7 @@ TryReferenceInit(Sema &S, Expr *Init, QualType DeclType,
   //   the argument expression. Any difference in top-level
   //   cv-qualification is subsumed by the initialization itself
   //   and does not constitute a conversion.
-  ICS = TryImplicitConversion(S, Init, DeclType, SuppressUserConversions,
+  ICS = TryImplicitConversion(S, Init, T1, SuppressUserConversions,
                               AllowedExplicit::None,
                               /*InOverloadResolution=*/false,
                               /*CStyle=*/false,
@@ -5450,6 +5450,11 @@ TryReferenceInit(Sema &S, Expr *Init, QualType DeclType,
       return ICS;
     }
 
+    if (isRValRef && ICS.UserDefined.ConversionFunction->getReturnType().isConstQualified()) {
+      ICS.setBad(BadConversionSequence::no_conversion, Init, DeclType);
+      return ICS;
+    }
+
     ICS.UserDefined.After.ReferenceBinding = true;
     ICS.UserDefined.After.IsLvalueReference = !isRValRef;
     ICS.UserDefined.After.BindsToFunctionLvalue = false;