E.g.
```
trait Trait {
type Item: SomeOtherTrait;
}
```
Note that these don't simply desugar to where clauses; as I understand it, where
clauses have to be proved by the *user* of the trait, but these bounds are proved
by the *implementor*. (Also, where clauses on associated types are unstable.)
Like `Iterator<Item: SomeTrait>`.
This is an unstable feature, but it's used in the standard library e.g. in the
definition of Flatten, so we can't get away with not implementing it :)
3938: fix missing match arm false positive r=flodiebold a=JoshMcguigan
This fixes#3932 by skipping the missing match arm diagnostic in the case any of the match arms don't type check properly against the match expression.
I think this is the appropriate behavior for this diagnostic, since `is_useful` relies on all match arms being well formed, and the case of a malformed match arm should probably be handled by a different diagnostic.
Co-authored-by: Josh Mcguigan <joshmcg88@gmail.com>
3905: add ellipsis field to hir pat record r=matklad a=JoshMcguigan
This PR corrects a `fixme`, adding an `ellipsis` field to the hir `Pat::Record` type. It will also be unlock some useful follow on work for #3894.
Additionally it adds a diagnostic for missing fields in record patterns.
~~Marking as a draft because I don't have any tests, and a small amount of manual testing on my branch from #3894 suggests it might *not* be working. Any thoughts on how I can best test this, or else pointers on where I might be going wrong?~~
Co-authored-by: Josh Mcguigan <joshmcg88@gmail.com>
Chalk now panics if we don't implement these methods and run with CHALK_DEBUG,
so I thought I'd try to implement them 'properly'. Sadly, it seems impossible to
do without transmuting lifetimes somewhere. The problem is that we need a `&dyn
HirDatabase` to get names etc., which we can't just put into TLS. I thought I
could just use `scoped-tls`, but that doesn't support references to unsized
types. So I put the `&dyn` into another struct and put the reference to *that*
into the TLS, but I have to transmute the lifetime to 'static for that to work.
3918: Add support for feature attributes in struct literal r=matklad a=bnjjj
As promised here is the next PR to solve 2 different scenarios with feature flag on struct literal.
close#3870
Co-authored-by: Benjamin Coenen <5719034+bnjjj@users.noreply.github.com>
The big change here is counting binders, not
variables (https://github.com/rust-lang/chalk/pull/360). We have to adapt to the
same scheme for our `Ty::Bound`. It's mostly fine though, even makes some things
more clear.
