feat: Implement ATPIT
Resolves#16584
Note: This implementation only works for ATPIT, not for TAIT.
The main hinderence that blocks the later is the defining sites of TAIT can be inner blocks like in;
```rust
type X = impl Default;
mod foo {
fn bar() -> super::X {
()
}
}
```
So, to figure out we are defining it or not, we should recursively probe for nested modules and bodies.
For ATPIT, we can just look into current body because `error[E0401]: can't use 'Self' from outer item` prevent such nested structures;
```rust
trait Foo {
type Item;
fn foo() -> Self::Item;
}
struct Bar;
impl Foo for Bar {
type Item = impl Default;
fn foo() -> Self::Item {
fn bar() -> Self::Item {
^^^^^^^^^^
|
use of `Self` from outer item
refer to the type directly here instead
5
}
bar()
}
}
```
But this implementation does not checks for unification of same ATPIT between different bodies, monomorphization, nor layout for similar reason. (But these can be done with lazyness if we can utilize something like "mutation of interned value" with `db`. I coundn't find such thing but I would appreciate it if such thing exists and you could let me know 😅)
internal: Record import origins in ItemScope and PerNS
This records the import items definitions come from in the module scope (as well as what an import resolves to in an ItemScope). It does ignore glob imports as thats a lot more work for little to no gain, glob imports act as if the importing items are "inlined" into the scope which suffices for almost all use cases I believe (to my knowledge, attributes on them have little effect).
There is still a lot of work needed to make this available to the IDE layer, but this lays out the ground work for havin IDE layer support.
cc https://github.com/rust-lang/rust-analyzer/issues/14079
the "add missing members" assists: implemented substitution of default values of const params
To achieve this, I've made `hir::ConstParamData` store the default values
Introduce macro sub-namespaces and `macro_use` prelude
This PR implements two mechanisms needed for correct macro name resolution: macro sub-namespace and `macro_use` prelude.
- [macro sub-namespaces][subns-ref]
Macros have two sub-namespaces: one for function-like macro and the other for those in attributes (including custom derive macros). When we're resolving a macro name for function-like macro, we should ignore non-function-like macros, and vice versa.
This helps resolve single-segment macro names because we can (and should, as rustc does) fallback to names in preludes when the name in the current module scope is in different sub-namespace.
- [`macro_use` prelude][prelude-ref]
`#[macro_use]`'d extern crate declarations (including the standard library) bring their macros into scope, but they should not be prioritized over local macros (those defined in place and those explicitly imported).
We have been bringing them into legacy (textual) macro scope, which has the highest precedence in name resolution. This PR introduces the `macro_use` prelude in crate-level `DefMap`s, whose precedence is lower than local macros but higher than the standard library prelude.
The first 3 commits are drive-by fixes/refactors.
Fixes#8828 (prelude)
Fixes#12505 (prelude)
Fixes#12734 (prelude)
Fixes#13683 (prelude)
Fixes#13821 (prelude)
Fixes#13974 (prelude)
Fixes#14254 (namespace)
[subns-ref]: https://doc.rust-lang.org/reference/names/namespaces.html#sub-namespaces
[prelude-ref]: https://doc.rust-lang.org/reference/names/preludes.html#macro_use-prelude
