r268543 - in /trunk/libstdc++-v3: ChangeLog inc...

[redi@gcc.gnu.org]

Author: redi
Date: Tue Feb  5 15:45:24 2019
New Revision: 268543

URL: https://gcc.gnu.org/viewcvs?rev=268543&root=gcc&view=rev
Log:
PR libstdc++/89194 untangle is_convertible and is_nothrow_convertible

The additional logic added to __is_convertible_helper in order to
support is_nothrow_convertible makes some uses of is_convertible
ill-formed. This appears to be due to PR c++/87603, but can be avoided
just by defining a separate helper for is_nothrow_convertible. The same
problems are likely to still exist for is_nothrow_convertible, but that
is new and so won't cause regressions for existing users of
is_convertible.

	PR libstdc++/89194
	* include/std/type_traits (__is_convertible_helper)
	(__is_convertible_helper<_From, _To, false>): Revert changes to
	support is_nothrow_convertible.
	(__is_nt_convertible_helper): New helper.
	(is_nothrow_convertible): Use __is_nt_convertible_helper.

Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/std/type_traits