From: Barrett Adair (barrettellisadair_at_[hidden])
Date: 2020-07-03 15:34:39
It was recently brought to my attention that the variable template version
of boost::callable_traits::is_invocable was always broken. A fix has been
merged to match the non-variable version of the trait. I This is a minor
change. Can this be included in 1.74?
https://github.com/boostorg/callable_traits/commit/6da8b5a9b8b439f8e751191a1ead3b1aa5e57a56