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:
![2021-04-11_00-33-33](https://user-images.githubusercontent.com/5489149/114296006-b38e1000-9a5d-11eb-9112-807c01b8fd0a.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>
This adds a "Convert Into to From" assist, useful since clippy has
recently started adding lints on every `Into`.
It covers converting the signature, and converting any `self`/`Self`
references within the body to the correct types.
It does assume that every instance of `Into` can be converted to a
`From`, which I _think_ is the case now. Let me know if there's
something I'm not thinking of and I can try and make it smarter.