4246: Validate uses of self and super r=matklad a=djrenren
This change follows on the validation of the `crate` keyword in paths. It verifies the following things:
`super`:
- May only be preceded by other `super` segments
- If in a `UseItem` then all semantically preceding paths also consist only of `super`
`self`
- May only be the start of a path
Just a note, a couple times while working on this I found myself really wanting a Visitor of some sort so that I could traverse descendants while skipping sub-trees that are unimportant. Iterators don't really work for this, so as you can see I reached for recursion. Considering paths are generally small a fancy debounced visitor probably isn't important but figured I'd say something in case we had something like this lying around and I wasn't using it.
Co-authored-by: John Renner <john@jrenner.net>
4178: Validate the location of `crate` in paths r=matklad a=djrenren
**This solution does not fully handle `use` statements. See below**
This pull requests implements simple validation of usages of the `crate` keyword in `Path`s. Specifically it validates that:
- If a `PathSegment` is starts with the `crate` keyword, it is also the first segment of the `Path`
- All other usages of `crate` in `Path`s are considered errors.
This aligns with `rustc`'s rules. Unlike rustc this implementation does not issue a special error message in the case of `::crate` but it does catch the error.
Furthermore, this change does not cover all error cases. Specifically the following is not caught:
```rust
use foo::{crate}
```
This is because this check is context sensitive. From an AST perspective, `crate` is the root of the `Path`. Only by inspecting the full `UseItem` do we see that it is not in fact the root. This problem becomes worse because `UseTree`s are allowed to be arbitrarily nested:
```rust
use {crate, {{crate, foo::{crate}}}
```
So this is a hard problem to solve without essentially a breadth-first search. In a traditional compiler, I'd say this error is most easily found during the AST -> HIR conversion pass but within rust-analyzer I'm not sure where it belongs.
Under the implementation in this PR, such errors are ignored so we're *more correct* just not *entirely correct*.
Co-authored-by: John Renner <john@jrenner.net>
todo!() "Indicates unfinished code" (https://doc.rust-lang.org/std/macro.todo.html)
Rust documentation provides further clarification:
> The difference between unimplemented! and todo! is that while todo!
> conveys an intent of implementing the functionality later and the
> message is "not yet implemented", unimplemented! makes no such claims.
todo!() seems more appropriate for assists that insert missing impls.
