[Bug c++/71377] SFINAE expression compiles, but it should not because of 14.5.5p8

[michele.caini at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71377

--- Comment #2 from Michele Caini <michele.caini at gmail dot com> ---
Right, got it.
Actually it's more like a complex way of writing a static assert.
Should it be considered a bug anyway? I mean, it's correct for GCC to accept it
or it should reject the code?
I'm not skilled enough to say how the standard applies in this case, I'm sorry.