Fix a couple weird implicit lookup cases.
Avoid illegal variance in traverseImpls.

(cherry picked from commit 6332266abf8ab3f0477c0d4cebfed17fa8f46069)
Avoid illegal variance in bitraverseImpls.

(cherry picked from commit 7a9d7670dfa06c8581348bf7d4ae8ff3cfd3db1f)