async/await
This PR implements `async`/`await` syntax for `async fn` in Rust 2015 and `async` closures and `async` blocks in Rust 2018 (tracking issue: https://github.com/rust-lang/rust/issues/50547). Limitations: non-`move` async closures with arguments are currently not supported, nor are `async fn` with multiple different input lifetimes. These limitations are not fundamental and will be removed in the future, however I'd like to go ahead and get this PR merged so we can start experimenting with this in combination with futures 0.3.
Based on https://github.com/rust-lang/rust/pull/51414.
cc @petrochenkov for parsing changes.
r? @eddyb
This is gated on edition 2018 & the `async_await` feature gate.
The parser will accept `async fn` and `async unsafe fn` as fn
items. Along the same lines as `const fn`, only `async unsafe fn`
is permitted, not `unsafe async fn`.The parser will not accept
`async` functions as trait methods.
To do a little code clean up, four fields of the function type
struct have been merged into the new `FnHeader` struct: constness,
asyncness, unsafety, and ABI.
Also, a small bug in HIR printing is fixed: it previously printed
`const unsafe fn` as `unsafe const fn`, which is grammatically
incorrect.
The Great Generics Generalisation: HIR Edition
This is essentially a followup to https://github.com/rust-lang/rust/pull/45930, consolidating the use of separate lifetime and type vectors into single kinds vectors wherever possible. This is intended to provide more of the groundwork for const generics (https://github.com/rust-lang/rust/issues/44580).
r? @eddyb
cc @yodaldevoid
Add existential type definitions
Note: this does not allow creating named existential types, it just desugars `impl Trait` to a less (but still very) hacky version of actual `existential type` items.
r? @nikomatsakis
refactor: create multiple HIR items for imports
When lowering `use` statements into HIR, they get a `Def` of the thing they're pointing at. This is great for things that need to know what was just pulled into scope. However, this is a bit misleading, because a `use` statement can pull things from multiple namespaces if their names collide. This is a problem for rustdoc, because if there are a module and a function with the same name (for example) then it will only document the module import, because that's that the lowered `use` statement points to.
The current version of this PR does the following:
* Whenever the resolver comes across a `use` statement, it loads the definitions into a new `import_map` instead of the existing `def_map`. This keeps the resolutions per-namespace so that all the target definitions are available.
* When lowering `use` statements, it looks up the resolutions in the `import_map` and creates multiple `Item`s if there is more than one resolution.
* To ensure the `NodeId`s are properly tracked in the lowered module, they need to be created in the AST, and pulled out as needed if multiple resolutions are available.
Fixes https://github.com/rust-lang/rust/issues/34843
Add lint for intra link resolution failure
This PR is almost done, just remains this note:
```
note: requested on the command line with `-W intra-link-resolution-failure`
```
I have no idea why my lint is considered as being passed through command line and wasn't able to find where it was set. If anyone has an idea, it'd be very helpful!
cc @QuietMisdreavus
rustdoc: process cross-crate glob re-exports
Turns out, we were deliberately ignoring glob re-exports when they were occurring across crates, even though we were fully processing them for local re-exports. This will at least bring the two into parity.
Fixes https://github.com/rust-lang/rust/issues/51252
