[libcxx-commits] [PATCH] D116388: [libc++] Properly handle specializations of std::is_placeholder.

[Arthur O'Dwyer via Phabricator via libcxx-commits]

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Before this patch, the user needed to specialize both of `is_placeholder<MyType>` and `is_placeholder<const MyType>`.
After this patch, only the former is needed (although the latter is harmless if provided).

The new tests don't actually fail unless return type deduction is used, which is a C++14 feature. Specializing `is_placeholder` is still allowed in C++11, though.

All of the above applies to `is_bind_expression`, too.

Fixes https://github.com/llvm/llvm-project/issues/51095


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D116388

Files:
  libcxx/include/__functional/bind.h
  libcxx/test/std/utilities/function.objects/bind/func.bind/func.bind.isbind/is_bind_expression.pass.cpp
  libcxx/test/std/utilities/function.objects/bind/func.bind/func.bind.isbind/is_placeholder.pass.cpp
  libcxx/test/std/utilities/function.objects/bind/func.bind/func.bind.isbind/specialization.pass.cpp
  libcxx/test/std/utilities/function.objects/bind/func.bind/func.bind.isplace/specialization.pass.cpp

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