Review

9

com/google/javascript/jscomp/PeepholeRemoveDeadCode.java

tryFoldFor(Node)

class PeepholeRemoveDeadCode {
  /**
   * Removes FORs that always evaluate to false.
   */
  Node tryFoldFor(Node n) {
    Preconditions.checkArgument(n.getType() == Token.FOR);
    // If this is a FOR-IN loop skip it.
    if (NodeUtil.isForIn(n)) {
      return n;
    }

    Node init = n.getFirstChild();
    Node cond = init.getNext();
    Node increment = cond.getNext();

    if (init.getType() != Token.EMPTY && init.getType() != Token.VAR) {
      init = trySimpilifyUnusedResult(init, false);
    }

    if (increment.getType() != Token.EMPTY) {
      increment = trySimpilifyUnusedResult(increment, false);
    }

    // There is an initializer skip it
    if (n.getFirstChild().getType() != Token.EMPTY) {
      return n;
    }

    if (NodeUtil.getBooleanValue(cond) != TernaryValue.FALSE) {
      return n;
    }

    NodeUtil.redeclareVarsInsideBranch(n);
    NodeUtil.removeChild(n.getParent(), n);
    reportCodeChange();
    return null;
  }

}