Fixup path fragments upon MBE transcription
Fixes#14367
There are roughly two types of paths: paths in expression context, where a separator `::` between an identifier and its following generic argument list is mandatory, and paths in type context, where `::` can be omitted.
Unlike rustc, we need to transform the parsed fragments back into tokens during transcription. When the matched path fragment is a type-context path and is transcribed as an expression-context path, verbatim transcription would cause a syntax error.
This PR fixes up path fragments by inserting `::` to make sure they are syntactically correct in all contexts. Note that this works because expression-context paths are a strict superset of type-context paths.
internal: Format let-else
As nightly finally got support for it I went ahead and formatted r-a with the latest nightly, then with the latest stable (in case other stuff changed)
Clean up `ImportMap`
There are several things in `hir_def::import_map` that are never used. This PR removes them and restructures the code. Namely:
- Removes `Query::name_only`, because it's *always* true.
- Because of this, we never took advantage of storing items' full path. This PR removes `ImportPath` and changes `ImportInfo` to only store items' name, which should reduce the memory consumption to some extent.
- Removes `SearchMode::Contains` for `Query` because it's never used.
- Merges `Query::assoc_items_only` and `Query::exclude_import_kinds` into `Query::assoc_mode`, because the latter is never used besides filtering associated items out.
Best reviewed one commit at a time. I made sure each commit passes full test suite. I can squash the first three commits if needed.
Use anonymous lifetime where possible
Because anonymous lifetimes are *super* cool.
More seriously, I believe anonymous lifetimes, especially those in impl headers, reduce cognitive load to a certain extent because they usually signify that they are not relevant in the signature of the methods within (or that we can apply the usual lifetime elision rules even if they are relevant).
Fix runnable detection for `#[tokio::test]`
fix#15141
It is hacky, and it wouldn't work for e.g. this case:
```Rust
use ::core::prelude;
#[prelude::v1::test]
fn foo() {
}
```
But it works for the tokio case. We should use the name resolution here somehow, and after that we should probably also get rid of the ast based `test_related_attribute` function.
