[PATCH] D122119: [C++20][Modules] Adjust handling of exports of namespaces and using-decls.

[Iain Sandoe via Phabricator via cfe-commits]

iains created this revision.
Herald added a project: All.
iains added reviewers: rsmith, urnathan, ChuanqiXu.
iains added a subscriber: clang-modules.
iains published this revision for review.
iains added a comment.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

this covers most of the tests from the standard section 10.3 (one to follow that has an additional dependency on header units)

note the change in the "cannot export redeclaration 'xxxx here since the previous declaration" errors to include a more specific reason than before.


This adjusts the handling for:

export module  M;

export namespace {};

export namespace N {};
export using namespace N;

In the first case, we were allowing empty anonymous namespaces
as part of an extension allowing empty top-level entities, but that seems
inappropriate in this case, since the linkage would be internal for the
anonymous namespace.  We now report an error for this.

The second case was producing a warning diagnostic that this was
accepted as an extension - however the C++20 standard does allow this
as well-formed.

In the third case we keep the current practice that this is accepted with a
warning (as an extension). The C++20 standard says it's an error.

We also ensure that using decls are only applied to items with external linkage.

This adjusts error messages for exports involving redeclarations in modules to
be more specific about the reason that the decl has been rejected.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D122119

Files:
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaDecl.cpp
  clang/lib/Sema/SemaModule.cpp
  clang/test/CXX/module/module.interface/p3.cpp
  clang/test/CXX/module/module.interface/p5.cpp
  clang/test/CXX/module/module.interface/p6.cpp
  clang/test/Modules/cxx20-10-2-ex1.cpp
  clang/test/Modules/cxx20-10-2-ex3.cpp
  clang/test/Modules/cxx20-10-2-ex4.cpp
  clang/test/Modules/cxx20-10-2-ex5.cpp
  clang/test/Modules/cxx20-10-2-ex6.cpp
  clang/test/Modules/cxx20-10-2-ex7.cpp

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D122119.416865.patch
Type: text/x-patch
Size: 22396 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20220321/d4591701/attachment-0001.bin>