[Bug c++/68926] [4.9/5/6 Regression] decltype and sfinae to check for template instance availability fails to compile

[grygoriy.fuchedzhy at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68926

Grygoriy Fuchedzhy <grygoriy.fuchedzhy at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |jason at redhat dot com

--- Comment #4 from Grygoriy Fuchedzhy <grygoriy.fuchedzhy at gmail dot com> ---
Regression was introduced in git commit
6395f98e518629ec25c36a680a3ec080590fa949 (190653 svn).
Attached patch fixes it for me. However it is probably not a proper fix for it.