[Bug c++/63723] Narrowing conversion allowed in braced init list in SFINAE context

[tavianator at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63723

--- Comment #8 from Tavian Barnes <tavianator at gmail dot com> ---
Actually it is a regression: according to http://gcc.godbolt.org/, GCC 4.6.4
compiled it correctly with -std=c++0x and

  typedef decltype(helper<From, To>(0)) type;

instead of

  using type = decltype(helper<From, To>(0));

while still allowing

  int x{1.0};