Merge #6845

6845: Don't HirDisplay unknown types when displaying for source r=Veykril a=Veykril

Was wondering why the add missing impl assist didn't do anything here:
![Code_JCA1Qo0V9P](https://user-images.githubusercontent.com/3757771/101990300-7af44a80-3ca6-11eb-8431-e5eb4de4e78c.png)
Turns out me forgetting to set the Index::Idx type in the trait causes RA to panic due to it trying to to create an unparsable type in the `make` module.
Now we get this instead which imo is definitely better to have.
![Code_MUFPJUCULY](https://user-images.githubusercontent.com/3757771/101990347-c9094e00-3ca6-11eb-9c6a-146bddf64b7c.png)



Co-authored-by: Lukas Wirth <[email protected]>

1 files changed, 25 insertions, 0 deletions

diff --git a/crates/assists/src/handlers/add_missing_impl_members.rs b/crates/assists/src/handlers/add_missing_impl_members.rs
index bbb71e261..e413505d3 100644
--- a/crates/assists/src/handlers/add_missing_impl_members.rs
+++ b/crates/assists/src/handlers/add_missing_impl_members.rs
@@ -784,4 +784,29 @@ impl Test for () {
 "#,
         )
     }
+
+    #[test]
+    fn missing_generic_type() {
+        check_assist(
+            add_missing_impl_members,
+            r#"
+trait Foo<BAR> {
+    fn foo(&self, bar: BAR);
+}
+impl Foo for () {
+    <|>
+}
+"#,
+            r#"
+trait Foo<BAR> {
+    fn foo(&self, bar: BAR);
+}
+impl Foo for () {
+    fn foo(&self, bar: BAR) {
+        ${0:todo!()}
+    }
+}
+"#,
+        )
+    }
 }