Review

12

com/google/javascript/jscomp/NameAnalyzer.java

replaceTopLevelExpressionWithRhs(Node, Node)

class NameAnalyzer {
  /**
   * Simplify a toplevel expression, while preserving program
   * behavior.
   */
  private void replaceTopLevelExpressionWithRhs(Node parent, Node n) {
    // validate inputs
    switch (parent.getType()) {
      case Token.BLOCK:
      case Token.SCRIPT:
      case Token.FOR:
      case Token.LABEL:
        break;
      default:
        throw new IllegalArgumentException(
            "Unsupported parent node type in replaceWithRhs " +
            Token.name(parent.getType()));
    }

    switch (n.getType()) {
      case Token.EXPR_RESULT:
      case Token.FUNCTION:
      case Token.VAR:
        break;
      case Token.ASSIGN:
        Preconditions.checkArgument(
            parent.getType() == Token.FOR,
            "Unsupported assignment in replaceWithRhs. parent: " +
            Token.name(parent.getType()));
        break;
      default:
        throw new IllegalArgumentException(
            "Unsupported node type in replaceWithRhs " +
            Token.name(n.getType()));
    }

    // gather replacements
    List<Node> replacements = Lists.newArrayList();
    for (Node rhs : getRhsSubexpressions(n)) {
      replacements.addAll(getSideEffectNodes(rhs));
    }

    if (parent.getType() == Token.FOR) {
      // tweak replacements array s.t. it is a single expression node.
      if (replacements.isEmpty()) {
        replacements.add(new Node(Token.EMPTY));
      } else {
        Node expr = collapseReplacements(replacements);
        replacements.clear();
        replacements.add(expr);
      }
    }

    changeProxy.replaceWith(parent, n, replacements);
  }

}