[Bug c++/69139] [4.9/5/6 Regression] deduction failure with trailing return type in function template argument

[abutcher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69139

--- Comment #4 from Adam Butcher <abutcher at gcc dot gnu.org> ---
@TC: Good call.  The patch at
https://gcc.gnu.org/ml/gcc-patches/2016-02/msg00495.html doesn't handle cv/ref
qualifiers.  I've expanded the testcase locally and will fix up the look-ahead
solution to handle them.