[clang] [Clang] Fix a crash when incorrectly calling an explicit object member function template (PR #75913)

[via cfe-commits]

https://github.com/cor3ntin created https://github.com/llvm/llvm-project/pull/75913

Fixes #75732

>From ba38db9f60f8a22e2a08f866e3540527131e16fb Mon Sep 17 00:00:00 2001
From: Corentin Jabot <corentinjabot at gmail.com>
Date: Tue, 19 Dec 2023 09:53:38 +0100
Subject: [PATCH] [Clang] Fix a crash when incorrectly calling an explicit
 object member function template

Fixes #75732
---
 clang/lib/Sema/SemaExprMember.cpp          |  2 ++
 clang/test/SemaCXX/cxx2b-deducing-this.cpp | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/clang/lib/Sema/SemaExprMember.cpp b/clang/lib/Sema/SemaExprMember.cpp
index 473eea55bb6b19..0e932a1436d6e0 100644
--- a/clang/lib/Sema/SemaExprMember.cpp
+++ b/clang/lib/Sema/SemaExprMember.cpp
@@ -253,6 +253,8 @@ static void diagnoseInstanceReference(Sema &SemaRef,
     SemaRef.Diag(Loc, diag::err_member_call_without_object)
         << Range << /*static*/ 0;
   else {
+    if (auto *Tpl = dyn_cast<FunctionTemplateDecl>(Rep))
+      Rep = Tpl->getTemplatedDecl();
     const auto *Callee = dyn_cast<CXXMethodDecl>(Rep);
     auto Diag = SemaRef.Diag(Loc, diag::err_member_call_without_object)
                 << Range << Callee->isExplicitObjectMemberFunction();
diff --git a/clang/test/SemaCXX/cxx2b-deducing-this.cpp b/clang/test/SemaCXX/cxx2b-deducing-this.cpp
index 0033541fa322dc..aab35828096a8e 100644
--- a/clang/test/SemaCXX/cxx2b-deducing-this.cpp
+++ b/clang/test/SemaCXX/cxx2b-deducing-this.cpp
@@ -626,3 +626,13 @@ void test() {
 }
 
 }
+
+
+namespace GH75732 {
+auto serialize(auto&& archive, auto&& c){ }
+struct D {
+    auto serialize(this auto&& self, auto&& archive) {
+        serialize(archive, self); // expected-error {{call to explicit member function without an object argument}}
+    }
+};
+}