/** Collapse VARs and EXPR_RESULT node into FOR loop initializers where possible. */
private void maybeCollapseIntoForStatements(Node n, Node parent) {
// Only SCRIPT, BLOCK, and LABELs can have FORs that can be collapsed into.
// LABELs are not supported here.
if (parent == null || !NodeUtil.isStatementBlock(parent)) {
return;
}
// Is the current node something that can be in a for loop initializer?
if (!NodeUtil.isExpressionNode(n) && !NodeUtil.isVar(n)) {
return;
}
// Is the next statement a valid FOR?
Node nextSibling = n.getNext();
if (nextSibling != null
&& nextSibling.getType() == Token.FOR
&& !NodeUtil.isForIn(nextSibling)
&& nextSibling.getFirstChild().getType() == Token.EMPTY) {
// Does the current node contain an in operator? If so, embedding
// the expression in a for loop can cause some Javascript parsers (such
// as the Playstation 3's browser based on Access's NetFront
// browser) to fail to parse the code.
// See bug 1778863 for details.
if (NodeUtil.containsType(n, Token.IN)) {
return;
}
// Move the current node into the FOR loop initializer.
Node forNode = nextSibling;
Node oldInitializer = forNode.getFirstChild();
parent.removeChild(n);
Node newInitializer;
if (NodeUtil.isVar(n)) {
newInitializer = n;
} else {
// Extract the expression from EXPR_RESULT node.
Preconditions.checkState(n.hasOneChild());
newInitializer = n.getFirstChild();
n.removeChild(newInitializer);
}
forNode.replaceChild(oldInitializer, newInitializer);
compiler.reportCodeChange();
}
}
/**
* @param n The node in question.
* @param cfgNode The node to add
* @param conditional true if the definition is not always executed.
*/
private void computeMustDef(Node n, Node cfgNode, MustDef output, boolean conditional) {
switch (n.getType()) {
case Token.BLOCK:
case Token.FUNCTION:
return;
case Token.WHILE:
case Token.DO:
case Token.IF:
computeMustDef(NodeUtil.getConditionExpression(n), cfgNode, output, conditional);
return;
case Token.FOR:
if (!NodeUtil.isForIn(n)) {
computeMustDef(NodeUtil.getConditionExpression(n), cfgNode, output, conditional);
} else {
// for(x in y) {...}
Node lhs = n.getFirstChild();
Node rhs = lhs.getNext();
if (NodeUtil.isVar(lhs)) {
lhs = lhs.getLastChild(); // for(var x in y) {...}
}
if (NodeUtil.isName(lhs)) {
addToDefIfLocal(lhs.getString(), cfgNode, rhs, output);
}
}
return;
case Token.AND:
case Token.OR:
computeMustDef(n.getFirstChild(), cfgNode, output, conditional);
computeMustDef(n.getLastChild(), cfgNode, output, true);
return;
case Token.HOOK:
computeMustDef(n.getFirstChild(), cfgNode, output, conditional);
computeMustDef(n.getFirstChild().getNext(), cfgNode, output, true);
computeMustDef(n.getLastChild(), cfgNode, output, true);
return;
case Token.VAR:
for (Node c = n.getFirstChild(); c != null; c = c.getNext()) {
if (c.hasChildren()) {
computeMustDef(c.getFirstChild(), cfgNode, output, conditional);
addToDefIfLocal(c.getString(), conditional ? null : cfgNode, c.getFirstChild(), output);
}
}
return;
default:
if (NodeUtil.isAssignmentOp(n)) {
if (NodeUtil.isName(n.getFirstChild())) {
Node name = n.getFirstChild();
computeMustDef(name.getNext(), cfgNode, output, conditional);
addToDefIfLocal(
name.getString(), conditional ? null : cfgNode, n.getLastChild(), output);
return;
} else if (NodeUtil.isGet(n.getFirstChild())) {
// Treat all assignments to arguments as redefining the
// parameters itself.
Node obj = n.getFirstChild().getFirstChild();
if (NodeUtil.isName(obj) && "arguments".equals(obj.getString())) {
// TODO(user): More accuracy can be introduced
// ie: We know exactly what arguments[x] is if x is a constant
// number.
escapeParameters(output);
}
}
}
if (NodeUtil.isName(n) && "arguments".equals(n.getString())) {
escapeParameters(output);
}
// DEC and INC actually defines the variable.
if (n.getType() == Token.DEC || n.getType() == Token.INC) {
Node target = n.getFirstChild();
if (NodeUtil.isName(target)) {
addToDefIfLocal(target.getString(), conditional ? null : cfgNode, null, output);
return;
}
}
for (Node c = n.getFirstChild(); c != null; c = c.getNext()) {
computeMustDef(c, cfgNode, output, conditional);
}
}
}