[libcxx-commits] [PATCH] D108216: [libc++] Formulate _EnableIf in terms of std::enable_if

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

Quuxplusone requested changes to this revision.
Quuxplusone added inline comments.
This revision now requires changes to proceed.


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Comment at: libcxx/include/__functional/bind_front.h:41
 
-template <class _Fn, class... _Args, class = _EnableIf<
+template <class _Fn, class... _Args, class = enable_if_t<
     _And<
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(1) What do the respective error messages look like with GCC? MSVC? (I bet those compilers lack Clang's special cases.)
(2) Is it conceivable that we could just make Clang understand anything-of-the-general-form-of-`_EnableIf`, based on the class template's shape, instead of based on special-casing its name?
(3) If all else fails, could we keep using the spelling `_EnableIf`, and just define `_EnableIf` as an alias for `enable_if_t`? At least then it would be easy for anyone who cared about compile-time performance to just patch it in one place. (Arguably I bet it would do no harm for them to patch it at the `enable_if_t` level, and thus speed up even more things than just libc++ itself.) Also, it would make this patch a lot less invasive.
(4) Is this the camel's nose in the tent? Are you soon going to propose replacing `_If` with `conditional_t`? Do we want this?


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https://reviews.llvm.org/D108216