Only show first overload in a series of consecutive overload signatures

...for navigateTo.

Current semantics:
* If an overload lacks an implementation, go to the first overload.
* If an overload has any implementation, go to the first one.
* If there are any declarations between an implementation and any overload, this will split the series of overloads (note that this is invalid code).
we only fall through in certain condition. Could you comment more on this?