[Bug c++/79070] Unhelpful error message for ambiguous type in template parameter

[gccbugbjorn at fahller dot se]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79070

--- Comment #1 from Björn Fahller <gccbugbjorn at fahller dot se> ---
More info: adding an alias for a function signature involving the ambiguous Foo
in the above program gives a directly misleading error message:

using type = void(Foo);

c.cpp:12:18: error: expected ';' before '(' token
 using type = void(Foo);
                  ^