E.g. when there's a type mismatch on the return value of a function. To
fix this, we have to return the expected type as the type of the block
when there's a mismatch. That meant some IDE code that expected
otherwise had to be adapted, in particular the "add return type" assist.
For the "wrap in Ok/Some" quickfix, this sadly means it usually can't be applied
in all branches of an if expression at the same time anymore, because
there's a type mismatch for each branch that has the wrong type.
- don't return the receiver type from method resolution; instead just
return the autorefs/autoderefs that happened and repeat them. This
ensures all the effects like trait obligations and whatever we learned
about type variables from derefing them are actually applied. Also, it
allows us to get rid of `decanonicalize_ty`, which was just wrong in
principle.
- Autoderef itself now directly works with an inference table. Sadly
this has the effect of making it harder to use as an iterator, often
requiring manual `while let` loops. (rustc works around this by using
inner mutability in the inference context, so that things like unifying
types don't require a unique reference.)
- We now record the adjustments (autoref/deref) for method receivers
and index expressions, which we didn't before.
- Removed the redundant crate parameter from method resolution, since
the trait_env contains the crate as well.
- in the HIR API, the methods now take a scope to determine the trait env.
`Type` carries a trait env, but I think that's probably a bad decision
because it's easy to create it with the wrong env, e.g. by using
`Adt::ty`. This mostly didn't matter so far because
`iterate_method_candidates` took a crate parameter and ignored
`self.krate`, but the trait env would still have been wrong in those
cases, which I think would give some wrong results in some edge cases.
Fixes#10058.
Should fix#10090, #10046, #10179.
This is only a workaround, but the proper fix requires some bigger
refactoring (also related to fixing #10058), and this at least prevents
the crash.
9975: minor: Fix panic caused by #9966 r=flodiebold a=flodiebold
Chalk can introduce new type variables when doing lazy normalization, so we have to do the proper 'fudging' after all.
Co-authored-by: Florian Diebold <flodiebold@gmail.com>
