Example:

class C {
  int foo(int x) => x;
}

abstract class D {
  int foo(int x, [int y]);
}

class E extends C implements D {}

typedef int foo2(int x, [int y]);

main() {
  D d = new E();
  foo2 foo = d.foo;
  print(foo(2,2));
}

This should give a static warning since E is a non-static class that doesn't have a method matching the super-interface method D.foo.
It has an inherited method of the same name, but it's not matching (spec, section 7.10).

Gilad: Should this be a compilation error instead?