[libcxx-commits] [PATCH] D129229: [libc++] reference_wrapper does not define nested types as described in C++11/14

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This patch tries to fix the issue that the implementation of `reference_wrapper` does not define nested types as described in C++11/14 standard section 20.8.3/20.9.3 `[refwrap]`. When `T` is a class with a nested type `argument_type` `T1`, the template instantiation `reference_wrapper<T>` shall define a nested type named `argument_type` as a synonym for `T1`.  When `T` is a class with nested types named `first_argument_type` and `second_argument_type` of type `T1` and `T2`, the template instantiation `reference_wrapper<T>` shall define two nested types named `first_argument_type` and `second_argument_type` as synonyms for `T1` and `T2`, respectively. These types are deprecated in C++17 and removed in C++20.

The following test case demonstrates the issue.

  #include <functional>
  
  int main(void) {
    struct S{
      typedef int argument_type;
      typedef long first_argument_type;
      typedef float second_argument_type;
    };
    typedef std::reference_wrapper<S>::argument_type A1;
    typedef std::reference_wrapper<S>::first_argument_type A2;
    typedef std::reference_wrapper<S>::second_argument_type A3;
    static_assert(std::is_same<S::argument_type, A1>::value, "");
    static_assert(std::is_same<S::first_argument_type, A2>::value, "");
    static_assert(std::is_same<S::second_argument_type, A3>::value, "");
    return 0;
  }




Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129229

Files:
  libcxx/include/__functional/weak_result_type.h
  libcxx/test/libcxx/utilities/function.objects/refwrap/refwrap_types.pass.cpp
  libcxx/test/std/depr/depr.function.objects/depr.base/refwrap_types.depr.verify.cpp

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