From d89c6530fdb57da31f4750bf941a0e4a090c4474 Mon Sep 17 00:00:00 2001
From: Shafik Yaghmour <shafik.yaghmour@intel.com>
Date: Fri, 7 Apr 2023 08:57:24 -0700
Subject: [PATCH] [Clang] Fix filtering of inline namespaces for friend
 functions

PR D135370 implemented a performance improvement but it restricted the filtering
of declaration from inline namespace too much. In particular it did not filter
for the function template case.

This led to a regression and this PR removes that check.

This fixes: https://github.com/llvm/llvm-project/issues/61851

Differential Revision: https://reviews.llvm.org/D147762
---
 clang/lib/Sema/SemaTemplateInstantiateDecl.cpp |  2 +-
 clang/test/SemaTemplate/friend.cpp             | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index ba64591..f941882 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2293,7 +2293,7 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(
     // Filter out previous declarations that don't match the scope. The only
     // effect this has is to remove declarations found in inline namespaces
     // for friend declarations with unqualified names.
-    if (isFriend && !QualifierLoc && !FunctionTemplate) {
+    if (isFriend && !QualifierLoc) {
       SemaRef.FilterLookupForScope(Previous, DC, /*Scope=*/ nullptr,
                                    /*ConsiderLinkage=*/ true,
                                    QualifierLoc.hasQualifier());
diff --git a/clang/test/SemaTemplate/friend.cpp b/clang/test/SemaTemplate/friend.cpp
index 1427db0..b039f10 100644
--- a/clang/test/SemaTemplate/friend.cpp
+++ b/clang/test/SemaTemplate/friend.cpp
@@ -148,3 +148,21 @@ namespace PR42513_comment3 {
   template struct T<X1>;
   int n = f((X1*)nullptr); // expected-error {{cannot initialize a variable of type 'int' with an rvalue of type 'std::nullptr_t'}}
 }
+
+namespace GH61851 {
+namespace A {
+inline namespace B {
+  inline constexpr struct {} foo;
+}
+
+template <typename T>
+class Bar {
+  template <typename U>
+  friend void foo(U &&arg) {} // no diagnostic expected
+};
+}
+
+void foobar() {
+  A::Bar<int> b;
+}
+}
-- 
2.7.4