@VirellinVR In a room with just 23 people there is a greater than 50% chance that at least two people share the same urge to tell you about the birthday paradox
@fenbf Not an expert but if I were to guess:
[](auto x) -> decltype(x.invalid) { }
is a valid lambda-expression but
[](auto x) -> decltype(x.invalid) { } (t)
is an invalid function call expression.