@Override
  @NotNull
  public GrExpression getInvokedExpression() {
    for (PsiElement cur = this.getFirstChild(); cur != null; cur = cur.getNextSibling()) {
      if (cur instanceof GrExpression) return (GrExpression)cur;
    }
    throw new IncorrectOperationException("invoked expression must not be null");
  }
@Override
  @NotNull
  public GrExpression getInvokedExpression()