There are few things to note in the implementation:
First, this is a best-effort implementation. Mainly, type aliases may not be shown (due to their eager nature it's harder) and partial pathes (aka. hovering over `Struct` in `Struct::method`) are not supported at all.
Second, we only need to show substitutions in expression and pattern position, because in type position all generic arguments always have to be written explicitly.
This PR touches a lot of parts. But the main changes are changing
`hir_expand::Name` to be raw edition-dependently and only when necessary
(unrelated to how the user originally wrote the identifier),
and changing `is_keyword()` and `is_raw_identifier()` to be edition-aware
(this was done in #17896, but the FIXMEs were fixed here).
It is possible that I missed some cases, but most IDE parts should properly
escape (or not escape) identifiers now.
The rules of thumb are:
- If we show the identifier to the user, its rawness should be determined
by the edition of the edited crate. This is nice for IDE features,
but really important for changes we insert to the source code.
- For tests, I chose `Edition::CURRENT` (so we only have to (maybe) update
tests when an edition becomes stable, to avoid churn).
- For debugging tools (helper methods and logs), I used `Edition::LATEST`.
Support hovering limits for adts
Fix#17009
1. Currently, r-a supports limiting the number of struct fields displayed when hovering. This PR extends it to support enum variants and union fields. Since the display of these three (ADTs) is similar, this PR extends 'hover_show_structFields' to 'hover_show_adtFieldsOrVariants'.
2. This PR also resolved the problem that the layout of ADT was not restricted by display limitations when hovering on the Self type.
3. Additionally, this PR changes the default value of display limitations to `10` (instead of the original `null`), which helps users discover this feature.
