[pushmi.h] error: parentheses are required around this expression in a requires clause

[denchat]

I tried compiling PushmiTest.cpp with pushmi.h on compiler explorer.

gcc trunk and clang complained pushmi.h about

pushmi.h:496:15: error: parentheses are required around this expression in a requires clause

  (requires B == static_cast<bool>(This{})) constexpr

            ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

            (                              )

While gcc 9.3 compiled pushmi.h just fine with -fconcepts

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