The extra allocation for message should not matter here at all, but
using a static string is just as ergonomic, if not more, and there's
no reason to write deliberately slow code
2887: Initial auto import action implementation r=matklad a=SomeoneToIgnore
Closes https://github.com/rust-analyzer/rust-analyzer/issues/2180
Adds an auto import action implementation.
This implementation is not ideal and has a few limitations:
* The import search functionality should be moved into a separate crate accessible from ra_assists.
This requires a lot of changes and a preliminary design.
Currently the functionality is provided as a trait impl, more on that here: https://github.com/rust-analyzer/rust-analyzer/issues/2180#issuecomment-575690942
* Due to the design desicion from the previous item, no doctests are run for the new aciton (look for a new FIXME in the PR)
* For the same reason, I have to create the mock trait implementaion to test the assist
* Ideally, I think we should have this feature as a diagnostics (that detects an absense of an import) that has a corresponding quickfix action that gets evaluated on demand.
Curretly we perform the import search every time we resolve the import which looks suboptimal.
This requires `classify_name_ref` to be moved from ra_ide, so not done currently.
A few improvements to the imports mechanism to be considered later:
* Constants like `ra_syntax::SyntaxKind::NAME` are not imported, because they are not present in the database
* Method usages are not imported, they are found in the database, but `find_use_path` does not return any import paths for them
* Some import paths returned by the `find_use_path` method end up in `core::` or `alloc::` instead of `std:`, for example: `core::fmt::Debug` instead of `std::fmt::Debug`.
This is not an error techically, but still looks weird.
* No detection of cases where a trait should be imported in order to be able to call a method
* Improve `auto_import_text_edit` functionality: refactor it and move away from the place it is now, add better logic for merging the new import with already existing imports
Co-authored-by: Kirill Bulatov <mail4score@gmail.com>
