Prompted by
> One nit: I think we need to consider `Any` and `Unknown` and `Todo` as
all (gradually) equivalent to each other, and thus `type & Any` and
`type & Unknown` and `type & Todo` as also equivalent. The distinction
between `Any` vs `Unknown` vs `Todo` is entirely about
provenance/debugging, there is no type level distinction. (And I've been
wondering if the `Any` vs `Unknown` distinction is really worth it.)
The thought here is that _most_ places want to treat `Any`, `Unknown`,
and `Todo` identically. So this PR simplifies things by having a single
`Type::Any` variant, and moves the provenance part into a new `AnyType`
type. If you need to treat e.g. `Todo` differently, you still can by
pattern-matching into the `AnyType`. But if you don't, you can just use
`Type::Any(_)`.
(This would also allow us to (more easily) distinguish "unknown via an
unannotated value" from "unknown because of a typing error" should we
want to do that in the future)
---------
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: Carl Meyer <carl@astral.sh>
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