[clang] Add cxx scope if needed for requires clause.

[luken-google]

Summary

Fixes issue #55216.

[luken-google]

Fix clang-format errors

[luken-google]

Note that the following tests:

Builtins-i386-linux :: muldc3_test.c
SanitizerCommon-asan-i386-Linux :: Linux/crypt_r.cpp
SanitizerCommon-asan-i386-Linux :: Posix/crypt.cpp
SanitizerCommon-lsan-i386-Linux :: Linux/crypt_r.cpp
SanitizerCommon-lsan-i386-Linux :: Posix/crypt.cpp
SanitizerCommon-ubsan-i386-Linux :: Linux/crypt_r.cpp
SanitizerCommon-ubsan-i386-Linux :: Posix/crypt.cpp

Are failing at HEAD and at this base diff without this patch.

[ilya-biryukov]

Thanks for the fix. This looks ok to me, except that I am a bit suspicious of the fact that DeclaratorScopeObj is used somewhat rarely.
I suspect we might want a different guard class for this, e.g. something similar to InitializerScopeRAII.
But I do not enough of the details for the corresponding code to know what the implications of these choices are.

@aaron.ballman could you PTAL or suggest someone who can help review this change?

clang/lib/Parse/ParseTemplate.cpp

294–299

Merging ifs should produce simpler code.

[aaron.ballman]

FWIW, I think this looks correct as well. I've added some reviewers just in case there's something I've missed regarding concepts.

clang/lib/Parse/ParseTemplate.cpp

293–301

Can simplify even further with a new local.

[aaron.ballman]

Also, don't forget to add a release note since this is fixing an issue.

[erichkeane]

Like @ilya-biryukov , I don't really know enough of the uses of 'DeclaratorScopeObj ' to know if that is right, but other than Aaron's suggestions, I don't see anything to suggest.

[luken-google]

Responding to feedback.

[luken-google]

Thanks for the feedback and the code review. I've uploaded a new revision with the requested changes, PTAL.

[erichkeane]

clang/lib/Parse/ParseTemplate.cpp

293

Not sure about this type, should this be a reference?

[luken-google]

Make ScopeSpec a reference.

clang/lib/Parse/ParseTemplate.cpp

293

Mm, good point. Fixed.

[aaron.ballman]

LGTM! Do you need someone to commit on your behalf? If so, what name and email address would you like used for patch attribution?

clang/docs/ReleaseNotes.rst

177

clang/lib/Parse/ParseTemplate.cpp

293

Great catch!!

[luken-google]

Yes please, I'm hoping to earn committer rights with a series of C++20 patches :).
Name is Luke Nihlen, email is [e-mail], github ID is luken-google@.

Thanks!

[ilya-biryukov]

I will commit this on behalf of Luke.

clang/docs/ReleaseNotes.rst

- Consider explicitly defaulted constexpr/consteval special member function
   a function cannot appear in a constant expression.
   (C++14 [dcl.constexpr]p6 (CWG DR647/CWG DR1358))
 - Correctly defer dependent immediate function invocations until template instantiation.
   This fixes `GH55601 <https://github.com/llvm/llvm-project/issues/55601>`_.
 - Implemented "Conditionally Trivial Special Member Functions" (`P0848 <https://wg21.link/p0848r3>`_).
   Note: The handling of deleted functions is not yet compliant, as Clang
   does not implement `DR1496 <https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1496>`_
   and `DR1734 <https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1734>`_.
+- Class member variables are now in scope when parsing requires clauses. Fixes
+  `GH55216 <https://github.com/llvm/llvm-project/issues/55216>`_.
 
 
 
 C++2b Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
 
 CUDA/HIP Language Changes in Clang
 ----------------------------------
 
 Objective-C Language Changes in Clang

clang/lib/Parse/ParseTemplate.cpp

Decl *Parser::ParseSingleDeclarationAfterTemplate(
   llvm::TimeTraceScope TimeScope("ParseTemplate", [&]() {
     return std::string(DeclaratorInfo.getIdentifier() != nullptr
                            ? DeclaratorInfo.getIdentifier()->getName()
                            : "<unknown>");
   });
 
   LateParsedAttrList LateParsedAttrs(true);
   if (DeclaratorInfo.isFunctionDeclarator()) {
-    if (Tok.is(tok::kw_requires))
+    if (Tok.is(tok::kw_requires)) {
+      CXXScopeSpec &ScopeSpec = DeclaratorInfo.getCXXScopeSpec();
+      DeclaratorScopeObj DeclScopeObj(*this, ScopeSpec);
+      if (ScopeSpec.isValid() &&
+          Actions.ShouldEnterDeclaratorScope(getCurScope(), ScopeSpec))
+        DeclScopeObj.EnterDeclaratorScope();
       ParseTrailingRequiresClause(DeclaratorInfo);
+    }
 
     MaybeParseGNUAttributes(DeclaratorInfo, &LateParsedAttrs);
   }
 
   if (DeclaratorInfo.isFunctionDeclarator() &&
       isStartOfFunctionDefinition(DeclaratorInfo)) {
 
     // Function definitions are only allowed at file scope and in C++ classes.
     // The C++ inline method definition case is handled elsewhere, so we only
     // need to handle the file scope definition case.

clang/test/Parser/cxx-concepts-requires-clause.cpp

 // RUN: %clang_cc1 -std=c++2a -x c++ %s -verify
 // RUN: %clang_cc1 -std=c++2b -x c++ %s -verify
 
 // Test parsing of the optional requires-clause in a template-declaration.
 
 template <typename T> requires true
 void foo() { }
 
 template <typename T> requires (!0)
 struct A {
   void foo();
   struct AA;
   enum E : int;
   static int x;
+  static constexpr int z = 16;
 
   template <typename> requires true
   void Mfoo();
 
   template <typename> requires true
   struct M;
 
   template <typename> requires true
   static int Mx;
 
   template <typename TT> requires true
   using MQ = M<TT>;
+
+  constexpr int bazz() requires (z == 16);
 };
 
 template <typename T> requires (!0)
 void A<T>::foo() { }
 
 template <typename T> requires (!0)
 struct A<T>::AA { };
 

 int A<T>::Mx = 0;
 
 template <typename T> requires true
 int x = 0;
 
 template <typename T> requires true
 using Q = A<T>;
 
+template<typename T> requires (!0)
+constexpr int A<T>::bazz() requires (z == 16) { return z; }
+
 struct C {
   template <typename> requires true
   void Mfoo();
 
   template <typename> requires true
   struct M;
 
   template <typename> requires true