For example, the concept `movable`, as its counterpart, should
`meta::is_movable_type` exists in <meta> (in future C++)?
I know meta function lacks subsumption. But at least, should C++ in the
future add things like `std::meta::is_movable_type` ?

/* Furthermore, should meta function be subsumable? Sounds crazy huh?
`concept bool` might be a good type for this.
But I didn't encounter any reasonable use cases, subsumption is only
needed in template constraints, so I guess this is nonsense, almost .../

The reason I want `meta::is_movable_type` is that `movable` is
impossible to implement without a `template <...>`,
and templates are much more slower in compilation speed than concepts
and meta functions (not function templates).
It definitely doesn't require subsumption.

I don't know if somebody has already argued things like
`meta::is_movable_type` (a proposal, a compiler MVP, etc.).

I want to hear your thoughts.

Bingzhi