code: public Scope getDefiningScope() {
          Scope enclosing = getEnclosingScope();
          String name = getIdentifier();
          return enclosing == null ? null : enclosing.getDefiningScope(name);
      }
docs: Returns the {@link Scope} in which this {@code Name} is defined.
  @return the scope in which this name is defined, or {@code null}
  if it's not defined in the current lexical scope chain