Merge #3964 #3965 #3967

3964: Nicer Chalk debug logs r=matklad a=flodiebold

I'm looking at a lot of Chalk debug logs at the moment, so here's a few changes to make them slightly nicer...

3965: Implement inline associated type bounds r=matklad a=flodiebold

Like `Iterator<Item: SomeTrait>`.

This is an unstable feature, but it's used in the standard library e.g. in the definition of Flatten, so we can't get away with not implementing it :)

(This is cherry-picked from my recursive solver branch, where it works better, but I did manage to write a test that works with the current Chalk solver as well...)

3967: Handle `Self::Type` in trait definitions when referring to own associated type r=matklad a=flodiebold

It was implemented for other generic parameters for the trait, but not for `Self`.

(Last one off my recursive solver branch 😄 )

Co-authored-by: Florian Diebold <flodiebold@gmail.com>

crates/ra_hir_ty/src/tests/regression.rs

@@ -451,8 +451,7 @@ pub mod str {
 "#,
     );
 
-    // should be Option<char>, but currently not because of Chalk ambiguity problem
-    assert_eq!("(Option<{unknown}>, Option<{unknown}>)", super::type_at_pos(&db, pos));
+    assert_eq!("(Option<char>, Option<char>)", super::type_at_pos(&db, pos));
 }
 
 #[test]

crates/ra_hir_ty/src/tests/traits.rs

@@ -1803,7 +1803,7 @@ fn test<T, U>() where T::Item: Trait2, T: Trait<U::Item>, U: Trait<()> {
 }
 
 #[test]
-fn unselected_projection_on_trait_self() {
+fn unselected_projection_on_impl_self() {
     assert_snapshot!(infer(
         r#"
 //- /main.rs
@@ -1843,6 +1843,30 @@ impl Trait for S2 {
     "###);
 }
 
+#[test]
+fn unselected_projection_on_trait_self() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Trait {
+    type Item;
+
+    fn f(&self) -> Self::Item { loop {} }
+}
+
+struct S;
+impl Trait for S {
+    type Item = u32;
+}
+
+fn test() {
+    S.f()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "u32");
+}
+
 #[test]
 fn trait_impl_self_ty() {
     let t = type_at(
@@ -1923,6 +1947,53 @@ fn test<T, U>() where T: Trait<U::Item>, U: Trait<T::Item> {
     assert_eq!(t, "{unknown}");
 }
 
+#[test]
+fn inline_assoc_type_bounds_1() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Iterator {
+    type Item;
+}
+trait OtherTrait<T> {
+    fn foo(&self) -> T;
+}
+
+// workaround for Chalk assoc type normalization problems
+pub struct S<T>;
+impl<T: Iterator> Iterator for S<T> {
+    type Item = <T as Iterator>::Item;
+}
+
+fn test<I: Iterator<Item: OtherTrait<u32>>>() {
+    let x: <S<I> as Iterator>::Item;
+    x.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "u32");
+}
+
+#[test]
+fn inline_assoc_type_bounds_2() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Iterator {
+    type Item;
+}
+
+fn test<I: Iterator<Item: Iterator<Item = u32>>>() {
+    let x: <<I as Iterator>::Item as Iterator>::Item;
+    x<|>;
+}
+"#,
+    );
+    // assert_eq!(t, "u32");
+    // doesn't currently work, Chalk #234
+    assert_eq!(t, "{unknown}");
+}
+
 #[test]
 fn unify_impl_trait() {
     assert_snapshot!(