7900: show function params in completion detail r=matklad a=JoshMcguigan
This resolves#7842 by updating the detail for function completions from `-> T` to `fn(T, U) -> V`. I added an expicit unit test for this, `ide_completion::render::fn_detail_includes_args_and_return_type`, which passes.
Lots of other unit tests fail (~60 of them) due to this change, although I believe the failures are purely cosmetic (they were testing the exact format of this output). I'm happy to go update those tests, but before I do that I'd like to make sure this is in fact the format we want for the detail?
edit - I realized `UPDATE_EXPECT=1 cargo test` automatically updates `expect!` tests. Big 👍 to whoever worked on that! So I'll go ahead and update all these tests soon. But I still would like to confirm `fn(T, U) -> V` is the desired content in the `detail` field.
8000: Use hir formatter for hover text r=matklad a=oxalica
Fix#2765 , (should) fix#4665
Co-authored-by: Josh Mcguigan <joshmcg88@gmail.com>
Co-authored-by: oxalica <oxalicc@pm.me>
