[PATCH] D128921: [Sema] Merge C++20 concept definitions from different modules in same TU

[Ilya Biryukov via Phabricator via cfe-commits]

ilya-biryukov added a comment.

@erichkeane please let me know if you're the right person to review this.



================
Comment at: clang/lib/Sema/SemaTemplate.cpp:8674
     auto *Old = Previous.getRepresentativeDecl();
     Diag(NameLoc, isa<ConceptDecl>(Old) ? diag::err_redefinition :
          diag::err_redefinition_different_kind) << NewDecl->getDeclName();
----------------
Not sure if reporting the redefinition if `isSameEntity` returns false is the right approach here.
This leads to errors on definitions of something like:
```
// foo.h
template <class T> concept A = false;

// bar.h
template <class T, class U> concept A = true;

#include "foo.h"
#include "bar.h" // <-- redefinition error shown here
```

The alternative is the "ambiguous reference" error on the use of the concept. I will check what happens for variables and typedefs in that case and follow the same pattern.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D128921/new/

https://reviews.llvm.org/D128921