/** If this is an assign to a variable or its property, return it. Otherwise, return null. */
static Assign maybeCreateAssign(Node assignNode) {
Preconditions.checkState(NodeUtil.isAssignmentOp(assignNode));
// Skip one level of GETPROPs or GETELEMs.
//
// Don't skip more than one level, because then we get into
// situations where assigns to properties of properties will always
// trigger side-effects, and the variable they're on cannot be removed.
boolean isPropAssign = false;
Node current = assignNode.getFirstChild();
if (NodeUtil.isGet(current)) {
current = current.getFirstChild();
isPropAssign = true;
if (current.getType() == Token.GETPROP
&& current.getLastChild().getString().equals("prototype")) {
// Prototype properties sets should be considered like normal
// property sets.
current = current.getFirstChild();
}
}
if (current.getType() == Token.NAME) {
return new Assign(assignNode, current, isPropAssign);
}
return null;
}
boolean isLvalue() {
Node parent = getParent();
int parentType = parent.getType();
return (parentType == Token.VAR && nameNode.getFirstChild() != null)
|| parentType == Token.INC
|| parentType == Token.DEC
|| (NodeUtil.isAssignmentOp(parent)
&& parent.getFirstChild() == nameNode)
|| isLhsOfForInExpression(nameNode);
}
Assign(Node assignNode, Node nameNode, boolean isPropertyAssign) {
Preconditions.checkState(NodeUtil.isAssignmentOp(assignNode));
this.assignNode = assignNode;
this.nameNode = nameNode;
this.isPropertyAssign = isPropertyAssign;
this.mayHaveSecondarySideEffects =
assignNode.getParent().getType() != Token.EXPR_RESULT
|| NodeUtil.mayHaveSideEffects(assignNode.getFirstChild())
|| NodeUtil.mayHaveSideEffects(assignNode.getLastChild());
}
boolean isLvalue() {
Node parent = getParent();
int parentType = parent.getType();
return (parentType == Token.VAR && nameNode.getFirstChild() != null)
|| (parentType == Token.LET && nameNode.getFirstChild() != null)
|| (parentType == Token.CONST && nameNode.getFirstChild() != null)
|| (parentType == Token.DEFAULT_VALUE && parent.getFirstChild() == nameNode)
|| parentType == Token.INC
|| parentType == Token.DEC
|| parentType == Token.CATCH
|| (NodeUtil.isAssignmentOp(parent) && parent.getFirstChild() == nameNode)
|| isLhsOfEnhancedForExpression(nameNode)
|| NodeUtil.isLhsByDestructuring(nameNode);
}
/**
* @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);
}
}
}
