Basically, if we had something like `dyn Trait<T>` (where `T` is a type
parameter) in an impl we lowered that to `dyn Trait<^0.0>`, when it should be
`dyn Trait<^1.0>` because the `dyn` introduces a new binder. With one type
parameter, that's just wrong, with two, it'll lead to crashes.
3966: Add support for bounds on associated types in trait definitions r=matklad a=flodiebold
E.g.
```rust
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.)
(Another one from my recursive solver branch...)
3968: Remove format from syntax_bridge hot path r=matklad a=edwin0cheng
Although only around 1% speed up by running:
```
Measure-Command {start-process .\target\release\rust-analyzer "analysis-stats -q ." -NoNewWindow -wait}
```
Co-authored-by: Florian Diebold <flodiebold@gmail.com>
Co-authored-by: Edwin Cheng <edwin0cheng@gmail.com>
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.)
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.
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.
It improves compile time in `--release` mode quite a bit, it doesn't
really slow things down and, conceptually, it seems closer to what we
want the physical architecture to look like (we don't want to
monomorphise EVERYTHING in a single leaf crate).
It's not very different, except we can directly use Salsa IDs instead of casting
them. This means we need to refactor the handling of errors to get rid of
UNKNOWN_TRAIT though.
