[Bug c++/77914] Wrong lambda definition accepted

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77914

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 40578
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40578&action=edit
gcc7-pr77914.patch

So like this (untested)?