the behavior of the type system not only depends on the current
assumptions, but also the currentnphase of the compiler. This is
mostly necessary as we need to decide whether and how to reveal
opaque types. We track this via the `TypingMode`.
`Deref`/`DerefMut` can be useful, but they can also obfuscate. I don't
think they're worth it for `RegionConstraintCollector`. They're also not
present on the similar types `OpaqueTypeTable` and `TypeVariableTable`.
`LeakCheck` can own `mini_graph` and `rcc` instead of holding references
to them. This requires inlining `assign_scc_value` to avoid a borrowck
error, but that's fine because it has a single call site.
It's a weird method, and used weirdly:
- It's on `RegionConstraintCollector` but operates on
`RegionConstraintStorage`. So at both call sites we create a temporary
`RegionConstraintCollector`, using `with_log`, to call it.
- It `take`s just two of the six fields in `RegionConstraintStorage`.
At one of the two call sites we unnecessarily clone the entire
`RegionConstraintStorage` just to take those two fields.
This commit just inlines and removes it. We no longer need to `take` the
two fields, we can just use them directly.
`OutlivesEnvironment::new` can call `OutlivesEnvironment::with_bounds`
with an empty `extra_bounds`. And once that's done,
`OutlivesEnvironmentBuilder` has a single use and can be inlined and
removed into `OutlivesEnvironment::with_bounds`.
Remove `CombineFields`
This conflicts with #131263, but if this one lands first then perhaps #131263 could then go ahead and remove all the branching on solver in `TypeRelating`. We could perhaps then rename `TypeRelating` to `OldSolverRelating` or something, idk.
r? lcnr
`FixupError` is isomorphic with `TyOrConstInferVar`, so this commit
changes it to just be a wrapper around `TyOrConstInferVar`.
Also, move the `Display` impl for `FixupError` next to `FixupError`.
Three of the modules don't need to be `pub`, and then
`warn(unreachable_pub)` identifies a bunch more things that also
shouldn't be `pub`, plus a couple of things that are unused.
