MIssing info for bounds on associated types.

[Xanewok]

Originally created by @nrc (rust-dev-tools/rls-analysis#140):

[Xanewok]

What I assume is the example:

trait TraitBound {}

trait MyTrait {
    type AssocType: TraitBound; // <-- it'd be nice to get any info whatsoever on the `TraitBound` type here
}