Merge #8467

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)

--

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 <[email protected]>

1 files changed, 27 insertions, 0 deletions

diff --git a/crates/ide_assists/src/tests/generated.rs b/crates/ide_assists/src/tests/generated.rs
index 27a22ca10..41559b43a 100644
--- a/crates/ide_assists/src/tests/generated.rs
+++ b/crates/ide_assists/src/tests/generated.rs
@@ -552,6 +552,33 @@ impl Default for Example {
 }
 
 #[test]
+fn doctest_generate_deref() {
+    check_doc_test(
+        "generate_deref",
+        r#####"
+struct A;
+struct B {
+   $0a: A
+}
+"#####,
+        r#####"
+struct A;
+struct B {
+   a: A
+}
+
+impl std::ops::Deref for B {
+    type Target = A;
+
+    fn deref(&self) -> &Self::Target {
+        &self.a
+    }
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_generate_derive() {
     check_doc_test(
         "generate_derive",