The method resolution diagnostic simplification framework doesn't work with generic calls, even when the cause of the mismatch does not depend on inference variables:

<Z> void m(List<Z> z, List<String> ls) { }

void test(List<Integer> li) {
m(null, li);
}

error is this:

Main.java:6: error: method m in class Foo cannot be applied to given types;
m(null, li);
^
  required: List<Z>,List<String>
  found: <null>,List<Integer>
  reason: cannot infer type-variable(s) Z
    (argument mismatch; List<Integer> cannot be converted to List<String>)
  where Z is a type-variable:
    Z extends Object declared in method <Z>m(List<Z>,List<String>)

When it could have been simplified into something like:

Main.java:6: error: incompatible types: List<Integer> cannot be converted to List<String>
m(null, li);
^

Diamond related error messages also suffer from a similar issue.