This is a very small enhancement.

Suppose to have this code:

public class Declaration {
  public void method() {
    List a = null;
      a.add(new Declaration());
      perform();
    }
}

1. Put the caret on the method add call on line 4 like this:
   a.ad|d(new Declaration());
2. Press CTRL+O

Current behavior:
The Go To Type popup is opened and the field TypeName is prefilled with "add" because the cursor is placed on the method add(..) call.

Enhancement suggested:
The Go To Type popup is opened and the field TypeName is prefilled with "List" because the cursor is placed on the method add(..) that is called on "a" that is an instance of "List".
This could be applied in general also when a variable name is selected (except for primitive types in which case the field should be prefilled with an empty string and not with the name of the variable)