From 90d4cbb87ce297d93159d39528767f5f46aa4da4 Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov <serebrennikov.vladislav@gmail.com>
Date: Thu, 8 Dec 2022 21:03:42 +0300
Subject: [PATCH] [clang] Add test for CWG418

P1787: //[[ https://cplusplus.github.io/CWG/issues/418.html | CWG418 ]] is resolved by trivial rephrasing along with that necessary for the new using-declaration interpretation.//
Wording: see changes to [dcl.fct.default]/9 and [over.match.best]/4.

[over.match.best]/4 includes [[ https://eel.is/c++draft/over.match.best#general-example-8 | an example ]] that is not properly diagnosed by Clang.

Reviewed By: #clang-language-wg, shafik

Differential Revision: https://reviews.llvm.org/D139429
---
 clang/test/CXX/drs/dr4xx.cpp | 44 ++++++++++++++++++++++++++++++++++++++++++++
 clang/www/cxx_dr_status.html |  2 +-
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/clang/test/CXX/drs/dr4xx.cpp b/clang/test/CXX/drs/dr4xx.cpp
index 1814f5a..3617af8 100644
--- a/clang/test/CXX/drs/dr4xx.cpp
+++ b/clang/test/CXX/drs/dr4xx.cpp
@@ -315,6 +315,50 @@ namespace dr417 { // dr417: no
   }
 }
 
+namespace dr418 { // dr418: no
+namespace example1 {
+void f1(int, int = 0);
+void f1(int = 0, int);
+
+void g() { f1(); }
+} // namespace example1
+
+namespace example2 {
+namespace A {
+void f2(int); // #dr418-f2-decl
+}
+namespace B {
+using A::f2;
+}
+namespace A {
+void f2(int = 3);
+}
+void g2() {
+  using B::f2;
+  f2(); // expected-error {{no matching function}}
+  // expected-note@#dr418-f2-decl {{requires 1 argument}}
+}
+} // namespace example2
+
+// example from [over.match.best]/4
+namespace example3 {
+namespace A {
+extern "C" void f(int = 5);
+}
+namespace B {
+extern "C" void f(int = 5);
+}
+
+using A::f;
+using B::f;
+
+void use() {
+  f(3);
+  f(); // FIXME: this should fail
+}
+} // namespace example3
+} // namespace dr418
+
 namespace dr420 { // dr420: yes
   template<typename T> struct ptr {
     T *operator->() const;
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index e8cb431..1c880bab 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -2547,7 +2547,7 @@ of class templates</td>
     <td><a href="https://wg21.link/cwg418">418</a></td>
     <td>CD6</td>
     <td>Imperfect wording on error on multiple default arguments on a called function</td>
-    <td class="none" align="center">Unknown</td>
+    <td class="none" align="center">No</td>
   </tr>
   <tr class="open" id="419">
     <td><a href="https://wg21.link/cwg419">419</a></td>
-- 
2.7.4