A type
MP meets the
layout mapping policy requirements
if for a type
E that is a specialization of
extents,
MP::mapping<E> is valid and denotes a type
X
that meets the layout mapping requirements (
[mdspan.layout.reqmts]), and
for which the
qualified-id X::layout_type is valid and
denotes the type
MP and
the
qualified-id X::extents_type denotes
E.