Add a test

tests/ui/associated-type-bounds/auxiliary/implied-predicates.rs

@@ -0,0 +1,7 @@
+pub trait Bar: Super<SuperAssoc: Bound> {}
+
+pub trait Super {
+    type SuperAssoc;
+}
+
+pub trait Bound {}

tests/ui/associated-type-bounds/implied-predicates.rs

@@ -0,0 +1,8 @@
+//@ aux-build:implied-predicates.rs
+
+extern crate implied_predicates;
+use implied_predicates::Bar;
+
+fn bar<B: Bar>() {}
+
+fn main() {}

tests/ui/associated-type-bounds/implied-predicates.stderr

@@ -0,0 +1,19 @@
+error[E0277]: the trait bound `<B as Super>::SuperAssoc: implied_predicates::Bound` is not satisfied
+  --> $DIR/implied-predicates.rs:6:11
+   |
+LL | fn bar<B: Bar>() {}
+   |           ^^^ the trait `implied_predicates::Bound` is not implemented for `<B as Super>::SuperAssoc`
+   |
+note: required by a bound in `Bar`
+  --> $DIR/auxiliary/implied-predicates.rs:1:34
+   |
+LL | pub trait Bar: Super<SuperAssoc: Bound> {}
+   |                                  ^^^^^ required by this bound in `Bar`
+help: consider further restricting the associated type
+   |
+LL | fn bar<B: Bar>() where <B as Super>::SuperAssoc: implied_predicates::Bound {}
+   |                  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.