[Bug c++/81211] Unhelpful error messages using template instance with non-copyable type argument

[srk31 at srcf dot ucam.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81211

--- Comment #3 from Stephen Kell <srk31 at srcf dot ucam.org> ---
I agree that this message is better (my bad for not trying a supported
release).

It'd be nice if I didn't have to guess that the reason it's not callable is
that I omitted the copy constructor. The rules for when constructors are
defaulted/deleted are baroque enough to catch anybody out from time to time.