Rollup merge of #84485 - marmeladema:trait-tests, r=jackh726

Add some associated type bounds tests

Closes #83017
Closes #81193

r? `@jackh726`

Author: JohnTitor

src/test/ui/associated-type-bounds/issue-81193.rs

@@ -0,0 +1,15 @@
+// check-pass
+
+#![feature(associated_type_bounds)]
+
+trait A<'a, 'b> {}
+
+trait B<'a, 'b, 'c> {}
+
+fn err<'u, 'a, F>()
+where
+    for<'b> F: Iterator<Item: for<'c> B<'a, 'b, 'c> + for<'c> A<'a, 'c>>,
+{
+}
+
+fn main() {}

src/test/ui/associated-type-bounds/issue-83017.rs

@@ -0,0 +1,39 @@
+#![feature(associated_type_bounds)]
+
+trait TraitA<'a> {
+    type AsA;
+}
+
+trait TraitB<'a, 'b> {
+    type AsB;
+}
+
+trait TraitC<'a, 'b, 'c> {}
+
+struct X;
+
+impl<'a, 'b, 'c> TraitC<'a, 'b, 'c> for X {}
+
+struct Y;
+
+impl<'a, 'b> TraitB<'a, 'b> for Y {
+    type AsB = X;
+}
+
+struct Z;
+
+impl<'a> TraitA<'a> for Z {
+    type AsA = Y;
+}
+
+fn foo<T>()
+where
+    for<'a> T: TraitA<'a, AsA: for<'b> TraitB<'a, 'b, AsB: for<'c> TraitC<'a, 'b, 'c>>>,
+{
+}
+
+fn main() {
+    foo::<Z>();
+    //~^ ERROR: the trait bound `for<'a, 'b> <Z as TraitA<'a>>::AsA: TraitB<'a, 'b>` is not satisfied
+    //~| ERROR: the trait bound `for<'a, 'b, 'c> <<Z as TraitA<'a>>::AsA as TraitB<'a, 'b>>::AsB: TraitC<'a, 'b, 'c>` is not satisfied
+}

src/test/ui/associated-type-bounds/issue-83017.stderr

@@ -0,0 +1,27 @@
+error[E0277]: the trait bound `for<'a, 'b> <Z as TraitA<'a>>::AsA: TraitB<'a, 'b>` is not satisfied
+  --> $DIR/issue-83017.rs:36:5
+   |
+LL | fn foo<T>()
+   |    --- required by a bound in this
+LL | where
+LL |     for<'a> T: TraitA<'a, AsA: for<'b> TraitB<'a, 'b, AsB: for<'c> TraitC<'a, 'b, 'c>>>,
+   |                                ------------------------------------------------------- required by this bound in `foo`
+...
+LL |     foo::<Z>();
+   |     ^^^^^^^^ the trait `for<'a, 'b> TraitB<'a, 'b>` is not implemented for `<Z as TraitA<'a>>::AsA`
+
+error[E0277]: the trait bound `for<'a, 'b, 'c> <<Z as TraitA<'a>>::AsA as TraitB<'a, 'b>>::AsB: TraitC<'a, 'b, 'c>` is not satisfied
+  --> $DIR/issue-83017.rs:36:5
+   |
+LL | fn foo<T>()
+   |    --- required by a bound in this
+LL | where
+LL |     for<'a> T: TraitA<'a, AsA: for<'b> TraitB<'a, 'b, AsB: for<'c> TraitC<'a, 'b, 'c>>>,
+   |                                                            -------------------------- required by this bound in `foo`
+...
+LL |     foo::<Z>();
+   |     ^^^^^^^^ the trait `for<'a, 'b, 'c> TraitC<'a, 'b, 'c>` is not implemented for `<<Z as TraitA<'a>>::AsA as TraitB<'a, 'b>>::AsB`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.