[Issue 13683] More precise error message for wrong lambda

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=13683

--- Comment #6 from Nick Treleaven <nick at geany.org> ---
> Without a compiler solution

BTW that would show the failing lambda with Phobos as is. The static assert PR
discussion said a compiler solution is needed rather than having to update
every template that accepts a lambda in Phobos.

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