Provides better help for the resolve failures inside an `impl` if the name matches:
- a field on the self type
- a method on the self type
- a method on the current trait ref (in a trait impl)
Not handling trait method suggestions if in a regular `impl` (as you can see on line 69 of the test), I believe it is possible though.
Also, provides a better message when `self` fails to resolve due to being a static method.
It's using some unsafe pointers to skip copying the larger structures (which are only used in error conditions); it's likely possible to get it working with lifetimes (all the useful refs should outlive the visitor calls) but I haven't really figured that out for this case. (can switch to copying code if wanted)
Closes#2356.
2a7a39191a