[Clang] Add extension+compatibility diags

Author: Sirraide

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -941,6 +941,12 @@ def warn_cxx98_compat_defaulted_deleted_function : Warning<
   "%select{defaulted|deleted}0 function definitions are incompatible with C++98">,
   InGroup<CXX98Compat>, DefaultIgnore;
 
+def ext_delete_with_message : ExtWarn<
+  "'= delete' with a message is a C++2c extension">, InGroup<CXX26>;
+def warn_cxx23_delete_with_message : Warning<
+  "'= delete' with a message is incompatible with C++ standards before C++2c">,
+  DefaultIgnore, InGroup<CXXPre26Compat>;
+
 // C++11 default member initialization
 def ext_nonstatic_member_init : ExtWarn<
   "default member initializer for non-static data member is a C++11 "

clang/lib/Parse/ParseCXXInlineMethods.cpp

@@ -95,6 +95,11 @@ NamedDecl *Parser::ParseCXXInlineMethodDef(
       StringLiteral *Message = ParseCXXDeletedFunctionMessage();
       Actions.SetDeclDeleted(FnD, KWLoc, Message);
       Delete = true;
+      if (Message)
+        Diag(Message->getBeginLoc(), getLangOpts().CPlusPlus26
+                                         ? diag::warn_cxx23_delete_with_message
+                                         : diag::ext_delete_with_message)
+            << Message->getSourceRange();
       if (auto *DeclAsFunction = dyn_cast<FunctionDecl>(FnD)) {
         DeclAsFunction->setRangeEnd(KWEndLoc);
       }

clang/lib/Parse/Parser.cpp

@@ -1417,6 +1417,11 @@ Decl *Parser::ParseFunctionDefinition(ParsingDeclarator &D,
           << 1 /* deleted */;
       BodyKind = Sema::FnBodyKind::Delete;
       DeletedMessage = ParseCXXDeletedFunctionMessage();
+      if (DeletedMessage)
+        Diag(DeletedMessage->getBeginLoc(),
+             getLangOpts().CPlusPlus26 ? diag::warn_cxx23_delete_with_message
+                                       : diag::ext_delete_with_message)
+            << DeletedMessage->getSourceRange();
     } else if (TryConsumeToken(tok::kw_default, KWLoc)) {
       Diag(KWLoc, getLangOpts().CPlusPlus11
                       ? diag::warn_cxx98_compat_defaulted_deleted_function

clang/test/Parser/cxx2c-delete-with-message.cpp

@@ -1,19 +1,21 @@
+// RUN: %clang_cc1 -std=c++23 -fsyntax-only -verify=expected,pre26 -pedantic %s
+// RUN: %clang_cc1 -std=c++2c -fsyntax-only -verify=expected,compat -Wpre-c++26-compat %s
 // RUN: %clang_cc1 -std=c++2c -fsyntax-only -verify %s
 
 struct S {
   void a() = delete;
   void b() = delete(; // expected-error {{expected string literal}} expected-error {{expected ')'}} expected-note {{to match this '('}}
   void c() = delete(); // expected-error {{expected string literal}}
   void d() = delete(42); // expected-error {{expected string literal}}
-  void e() = delete("foo"[0]); // expected-error {{expected ')'}} expected-note {{to match this '('}}
-  void f() = delete("foo");
+  void e() = delete("foo"[0]); // expected-error {{expected ')'}} expected-note {{to match this '('}} // pre26-warning {{'= delete' with a message is a C++2c extension}} compat-warning {{'= delete' with a message is incompatible with C++ standards before C++2c}}
+  void f() = delete("foo"); // pre26-warning {{'= delete' with a message is a C++2c extension}} compat-warning {{'= delete' with a message is incompatible with C++ standards before C++2c}}
 
-  S() = delete("foo");
-  ~S() = delete("foo");
-  S(const S&) = delete("foo");
-  S(S&&) = delete("foo");
-  S& operator=(const S&) = delete("foo");
-  S& operator=(S&&) = delete("foo");
+  S() = delete("foo"); // pre26-warning {{'= delete' with a message is a C++2c extension}} compat-warning {{'= delete' with a message is incompatible with C++ standards before C++2c}}
+  ~S() = delete("foo"); // pre26-warning {{'= delete' with a message is a C++2c extension}} compat-warning {{'= delete' with a message is incompatible with C++ standards before C++2c}}
+  S(const S&) = delete("foo"); // pre26-warning {{'= delete' with a message is a C++2c extension}} compat-warning {{'= delete' with a message is incompatible with C++ standards before C++2c}}
+  S(S&&) = delete("foo"); // pre26-warning {{'= delete' with a message is a C++2c extension}} compat-warning {{'= delete' with a message is incompatible with C++ standards before C++2c}}
+  S& operator=(const S&) = delete("foo"); // pre26-warning {{'= delete' with a message is a C++2c extension}} compat-warning {{'= delete' with a message is incompatible with C++ standards before C++2c}}
+  S& operator=(S&&) = delete("foo"); // pre26-warning {{'= delete' with a message is a C++2c extension}} compat-warning {{'= delete' with a message is incompatible with C++ standards before C++2c}}
 };
 
 struct T {
@@ -29,5 +31,5 @@ void a() = delete;
 void b() = delete(; // expected-error {{expected string literal}} expected-error {{expected ')'}} expected-note {{to match this '('}}
 void c() = delete(); // expected-error {{expected string literal}}
 void d() = delete(42); // expected-error {{expected string literal}}
-void e() = delete("foo"[0]); // expected-error {{expected ')'}} expected-note {{to match this '('}}
-void f() = delete("foo");
+void e() = delete("foo"[0]); // expected-error {{expected ')'}} expected-note {{to match this '('}} // pre26-warning {{'= delete' with a message is a C++2c extension}} compat-warning {{'= delete' with a message is incompatible with C++ standards before C++2c}}
+void f() = delete("foo"); // pre26-warning {{'= delete' with a message is a C++2c extension}} compat-warning {{'= delete' with a message is incompatible with C++ standards before C++2c}}