When referring to an associated type of a super trait, we used the substs of the subtrait. That led to the #4931 crash if the subtrait had less parameters, but it could also lead to other incorrectness if just the order was different. Fixes #4931.
When referring to an associated type of a super trait, we used the substs of the subtrait. That led to the #4931 crash if the subtrait had less parameters, but it could also lead to other incorrectness if just the order was different. Fixes #4931.