[PATCH] D103485: Fix a diagnoses-valid bug with using declarations

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman created this revision.
aaron.ballman added reviewers: rsmith, rjmccall, erichkeane.
aaron.ballman requested review of this revision.
Herald added a project: clang.

The following was found by a customer and is accepted by the other primary C++ compilers, but fails to compile in Clang:

  namespace sss {
  double foo(int, double);
  template <class T>
  T foo(T); // note: target of using declaration
  }  // namespace sss
  
  namespace oad {
  void foo();
  }
  
  namespace oad {
  using ::sss::foo;
  }
  
  namespace sss {
  using oad::foo; // note: using declaration
  }
  
  namespace sss {
  double foo(int, double) { return 0; }
  template <class T>
  T foo(T t) { // error: declaration conflicts with target of using declaration already in scope
    return t;
  }
  }  // namespace sss

I believe the issue is that `MergeFunctionDecl()` was calling `checkUsingShadowRedecl()` but only considering a `FunctionDecl` as a possible shadow and not `FunctionTemplateDecl`. The changes in this patch largely mirror how variable declarations were being handled by also catching `FunctionTemplateDecl`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D103485

Files:
  clang/lib/Sema/SemaDecl.cpp
  clang/test/CXX/modules-ts/basic/basic.def.odr/p6/global-vs-module.cpp
  clang/test/CXX/modules-ts/basic/basic.def.odr/p6/module-vs-global.cpp
  clang/test/CXX/modules-ts/basic/basic.def.odr/p6/module-vs-module.cpp
  clang/test/SemaCXX/using-decl-templates.cpp

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