@Nullable
  public static GrExpression extractReturnExpression(GrStatement returnStatement) {
    if (returnStatement instanceof GrReturnStatement) return ((GrReturnStatement)returnStatement).getReturnValue();
    if (returnStatement instanceof GrExpression) return (GrExpression)returnStatement;
    return null;
  }
@Nullable
  public static GrExpression extractReturnExpression(GrStatement returnStatement)