[clang] [clang][Sema] Bugfix for choosing the more specialized overload (PR #83279)

[via cfe-commits]

================
@@ -5333,38 +5333,37 @@ bool Sema::CheckIfFunctionSpecializationIsImmediate(FunctionDecl *FD,
   return false;
 }
 
-/// If this is a non-static member function,
-static void
-AddImplicitObjectParameterType(ASTContext &Context,
-                               CXXMethodDecl *Method,
-                               SmallVectorImpl<QualType> &ArgTypes) {
-  // C++11 [temp.func.order]p3:
-  //   [...] The new parameter is of type "reference to cv A," where cv are
-  //   the cv-qualifiers of the function template (if any) and A is
-  //   the class of which the function template is a member.
-  //
-  // The standard doesn't say explicitly, but we pick the appropriate kind of
-  // reference type based on [over.match.funcs]p4.
-  assert(Method && Method->isImplicitObjectMemberFunction() &&
-         "expected an implicit objet function");
-  QualType ArgTy = Context.getTypeDeclType(Method->getParent());
-  ArgTy = Context.getQualifiedType(ArgTy, Method->getMethodQualifiers());
-  if (Method->getRefQualifier() == RQ_RValue)
-    ArgTy = Context.getRValueReferenceType(ArgTy);
-  else
-    ArgTy = Context.getLValueReferenceType(ArgTy);
-  ArgTypes.push_back(ArgTy);
+static QualType GetImplicitObjectParameterType(ASTContext &Context,
+                                               const CXXMethodDecl *Method,
+                                               QualType RawType,
+                                               bool IsOtherRvr) {
+  // C++20 [temp.func.order]p3.1, p3.2:
+  //- The type X(M ) is “rvalue reference to cv A” if the optional ref-qualifier
+  //  of M is && or if M has no ref-qualifier and the positionally-corresponding
+  //  parameter of the other transformed template has rvalue reference type;
+  //  if this determination depends recursively upon whether X(M ) is an rvalue
+  //  reference type, it is not considered to have rvalue reference type.
+  //- Otherwise, X(M ) is “lvalue reference to cv A”.
----------------
whisperity wrote:

```suggestion
  // C++20 [temp.func.order]p3.1, p3.2:
  //  - The type X(M) is "rvalue reference to cv A" if the optional
  //    ref-qualifier of M is && or if M has no ref-qualifier and the
  //    positionally-corresponding parameter of the other transformed
  //    template has rvalue reference type; if this determination depends
  //    recursively upon whether X(M) is an rvalue reference type, it
  //    is not considered to have rvalue reference type.
  //
  //  - Otherwise, X(M) is "lvalue reference to cv A".
```

https://github.com/llvm/llvm-project/pull/83279