[clang] Add test for CWG255

[[https://wg21.link/p1787 | P1787]]: CWG255 (partially resolved by N3778 is resolved by generally specifying the restriction to usual deallocation functions.
Wording: In any case, any declarations other than of usual deallocation functions ([basic.stc.dynamic.deallocation]) are discarded. ([expr.delete]/9)

Reviewed By: #clang-language-wg, cor3ntin

Differential Revision: https://reviews.llvm.org/D147549

clang/test/CXX/drs/dr2xx.cpp

@@ -3,6 +3,7 @@
 // RUN: %clang_cc1 -std=c++14 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
 // RUN: %clang_cc1 -std=c++17 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
 // RUN: %clang_cc1 -std=c++20 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++2b %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
 
 // PR13819 -- __SIZE_TYPE__ is incompatible.
 typedef __SIZE_TYPE__ size_t; // expected-error 0-1 {{extension}}
@@ -692,6 +693,14 @@ namespace dr254 { // dr254: yes
   A<C>::type n; // expected-note {{instantiation of}}
 }
 
+namespace dr255 { // dr255: yes
+struct S {
+  void operator delete(void *){};
+  void operator delete(void *, int){};
+};
+void f(S *p) { delete p; }
+} // namespace dr255
+
 // dr256: dup 624
 
 namespace dr257 { // dr257: yes

clang/www/cxx_dr_status.html

@@ -1568,7 +1568,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://wg21.link/cwg255">255</a></td>
     <td>CD6</td>
     <td>Placement deallocation functions and lookup ambiguity</td>
-    <td class="none" align="center">Unknown</td>
+    <td class="full" align="center">Yes</td>
   </tr>
   <tr id="256">
     <td><a href="https://wg21.link/cwg256">256</a></td>