Extension instance members highlight doesn't take the exact extension into consideration

[FMorschel]

Consider this code:

abstract class C<T> {}

void f(C<int> v, C<String> s) {
  v.foo;
  s.foo;
}

extension on C<int> {
  int get foo => 0;
}

extension on C<String> {
  int get foo => 0;
}

Since both foo have the same signature (if one returned something else this doesn't happen) even though they are used separately, they all highlight together.

I'm unsure how hard it would be for occurrences to take this into consideration but I think we should probably think about fixing this.

This problem persists even with named extensions and extension overrides:

[FMorschel]

Okay, this seems to be an even bigger problem than I originally thought. The extended types don't need to be the same. I'll rename the issue.

extension on String {
  int get foo => 0;
}

extension on int {
  int get foo => 0;
}

void f(int v, String s) {
  v.foo;
  s.foo;
}

[FMorschel]

I'm looking into this

[FMorschel]

Here is the CL https://dart-review.googlesource.com/c/sdk/+/424688