[Clang][Sema] Ensure that the selected candidate for a member function explicit specialization is more constrained than all others (#101721)

The selection of the most constrained candidate for member function
explicit specializations introduced in #88963 does not check whether the
selected candidate is more constrained than all other candidates, which
can result in ambiguities being undiagnosed. This patch addresses the
issue.

1 files changed, 4 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 1f4bfa2..bab32b9 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7964,8 +7964,9 @@ NamedDecl *Sema::ActOnVariableDeclarator(
     D.setRedeclaration(CheckVariableDeclaration(NewVD, Previous));
   } else {
     // If this is an explicit specialization of a static data member, check it.
-    if (IsMemberSpecialization && !IsVariableTemplateSpecialization &&
-        !NewVD->isInvalidDecl() && CheckMemberSpecialization(NewVD, Previous))
+    if (IsMemberSpecialization && !IsVariableTemplate &&
+        !IsVariableTemplateSpecialization && !NewVD->isInvalidDecl() &&
+        CheckMemberSpecialization(NewVD, Previous))
       NewVD->setInvalidDecl();
 
     // Merge the decl with the existing one if appropriate.
@@ -10466,7 +10467,7 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
                                                 Previous))
           NewFD->setInvalidDecl();
       }
-    } else if (isMemberSpecialization && isa<CXXMethodDecl>(NewFD)) {
+    } else if (isMemberSpecialization && !FunctionTemplate) {
       if (CheckMemberSpecialization(NewFD, Previous))
           NewFD->setInvalidDecl();
     }