Fix assertion failure during operator overload resolution.

Author: katzdm

clang/lib/Sema/SemaConcept.cpp

@@ -1519,7 +1519,8 @@ bool Sema::IsAtLeastAsConstrained(NamedDecl *D1,
     auto IsExpectedEntity = [](const FunctionDecl *FD) {
       FunctionDecl::TemplatedKind Kind = FD->getTemplatedKind();
       return Kind == FunctionDecl::TK_NonTemplate ||
-             Kind == FunctionDecl::TK_FunctionTemplate;
+             Kind == FunctionDecl::TK_FunctionTemplate ||
+             Kind == FunctionDecl::TK_FunctionTemplateSpecialization;
     };
     const auto *FD2 = dyn_cast<FunctionDecl>(D2);
     (void)IsExpectedEntity;

clang/test/SemaCXX/PR98671.cpp

@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only %s -verify
+
+struct S {
+  operator int();
+
+  template <typename T>
+  operator T();
+};
+
+
+// Ensure that no assertion is raised when overload resolution fails while
+// choosing between an operator function template and an operator function.
+constexpr auto r = &S::operator int;
+// expected-error@-1 {{initializer of type '<overloaded function type>'}}