From 80dec2ecfffe30f86ecfeec8f553b16bb992c48b Mon Sep 17 00:00:00 2001
From: Shafik Yaghmour <shafik.yaghmour@intel.com>
Date: Thu, 14 Jul 2022 14:54:48 -0700
Subject: [PATCH] [Clang] Modify CXXMethodDecl::isMoveAssignmentOperator() to
 look through type sugar AcceptedPublic

Currently CXXMethodDecl::isMoveAssignmentOperator() does not look though type
sugar and so if the parameter is a type alias it will not be able to detect
that the method is a move assignment operator. This PR fixes that and adds a set
of tests that covers that we correctly detect special member functions when
defaulting or deleting them.

This fixes: https://github.com/llvm/llvm-project/issues/56456

Differential Revision: https://reviews.llvm.org/D129591
---
 clang/docs/ReleaseNotes.rst                   |  2 ++
 clang/lib/AST/DeclCXX.cpp                     |  2 +-
 .../SemaCXX/cxx0x-defaulted-functions.cpp     | 25 +++++++++++++++++++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index a02bc0a2f691..17c1dac2e82a 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -186,6 +186,8 @@ Bug Fixes
 - Clang now checks ODR violations when merging concepts from different modules.
   Note that this may possibly break existing code, and is done so intentionally.
   Fixes `Issue 56310 <https://github.com/llvm/llvm-project/issues/56310>`_.
+- Clang will now look through type sugar when checking a member function is a
+  move assignment operator. Fixes `Issue 56456 <https://github.com/llvm/llvm-project/issues/56456>`_.
 
 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index 6fc9a86bc3cf..c307cbe02ecf 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -2410,7 +2410,7 @@ bool CXXMethodDecl::isMoveAssignmentOperator() const {
     return false;
 
   QualType ParamType = getParamDecl(0)->getType();
-  if (!isa<RValueReferenceType>(ParamType))
+  if (!ParamType->isRValueReferenceType())
     return false;
   ParamType = ParamType->getPointeeType();
 
diff --git a/clang/test/SemaCXX/cxx0x-defaulted-functions.cpp b/clang/test/SemaCXX/cxx0x-defaulted-functions.cpp
index 25a40ef49401..73916fd3027e 100644
--- a/clang/test/SemaCXX/cxx0x-defaulted-functions.cpp
+++ b/clang/test/SemaCXX/cxx0x-defaulted-functions.cpp
@@ -259,3 +259,28 @@ namespace P1286R2 {
 
   static_assert(noexcept(A::B()), "");
 }
+
+namespace GH56456 {
+template <typename T>
+using RC=T const&;
+template <typename T>
+using RV=T&;
+template <typename T>
+using RM=T&&;
+
+struct A {
+  A(RC<A>) = default;
+  A(RM<A>) = default;
+
+  auto operator=(RC<A>) -> RV<A> = default;
+  auto operator=(RM<A>) -> RV<A> = default;
+};
+
+struct B {
+  B (RC<B>) = delete;
+  B (RM<B>) = delete;
+
+  auto operator = (RC<B>) -> RV<B> = delete;
+  auto operator = (RM<B>) -> RV<B> = delete;
+};
+}