private static List<Expression> asArgumentList(Expression arguments) {
    // MethodCallExpression.getArguments() may return an ArgumentListExpression,
    // a TupleExpression that wraps a NamedArgumentListExpression,
    // or (at least in 1.6) a NamedArgumentListExpression

    if (arguments instanceof NamedArgumentListExpression)
      // return same result as for NamedArgumentListExpression wrapped in TupleExpression
      return singletonList(arguments);

    return (arguments == null) ? null : ((TupleExpression) arguments).getExpressions();
  }
Tells if the source position for the given AST node is plausible.
Does not imply that the source position is correct.

@param node an AST node
@return <tt>true</tt> iff the AST node has a plausible source position
spock-core/src/main/java/org/spockframework/compiler/AstUtil.java