8467: Adds impl Deref assist r=jhgg a=jhgg
This PR adds a new `generate_deref` assist that automatically generates a deref impl for a given struct field.
Check out this gif:
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I have a few Q's:
- [x] Should I write more tests, if so, what precisely should I test for?
- [x] I have an inline question on line 65, can someone provide guidance? :)
- [x] I can implement this for `ast::TupleField` too. But should it be a separate assist fn, or should I try and jam both into the `generate_deref`?
- [x] I want to follow this up with an assist on `impl $0Deref for T {` which would automatically generate a `DerefMut` impl that mirrors the Deref as well, however, I could probably use some pointers on how to do that, since I'll have to reach into the ast of `fn deref` to grab the field that it's referencing for the `DerefMut` impl.
Co-authored-by: jake <jh@discordapp.com>
