/** 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;
}
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());
}