private Node tryFoldUnaryOperator(Node n) {
Preconditions.checkState(n.hasOneChild(), n);
Node left = n.getFirstChild();
Node parent = n.getParent();
if (left == null) {
return n;
}
TernaryValue leftVal = NodeUtil.getPureBooleanValue(left);
if (leftVal == TernaryValue.UNKNOWN) {
return n;
}
switch (n.getType()) {
case NOT:
// Don't fold !0 and !1 back to false.
if (late && left.isNumber()) {
double numValue = left.getDouble();
if (numValue == 0 || numValue == 1) {
return n;
}
}
Node replacementNode = NodeUtil.booleanNode(!leftVal.toBoolean(true));
parent.replaceChild(n, replacementNode);
reportCodeChange();
return replacementNode;
case POS:
if (NodeUtil.isNumericResult(left)) {
// POS does nothing to numeric values.
parent.replaceChild(n, left.detachFromParent());
reportCodeChange();
return left;
}
return n;
case NEG:
if (left.isName()) {
if (left.getString().equals("Infinity")) {
// "-Infinity" is valid and a literal, don't modify it.
return n;
} else if (left.getString().equals("NaN")) {
// "-NaN" is "NaN".
n.removeChild(left);
parent.replaceChild(n, left);
reportCodeChange();
return left;
}
}
if (left.isNumber()) {
double negNum = -left.getDouble();
Node negNumNode = IR.number(negNum);
parent.replaceChild(n, negNumNode);
reportCodeChange();
return negNumNode;
} else {
// left is not a number node, so do not replace, but warn the
// user because they can't be doing anything good
report(NEGATING_A_NON_NUMBER_ERROR, left);
return n;
}
case BITNOT:
try {
double val = left.getDouble();
if (val >= Integer.MIN_VALUE && val <= Integer.MAX_VALUE) {
int intVal = (int) val;
if (intVal == val) {
Node notIntValNode = IR.number(~intVal);
parent.replaceChild(n, notIntValNode);
reportCodeChange();
return notIntValNode;
} else {
report(FRACTIONAL_BITWISE_OPERAND, left);
return n;
}
} else {
report(BITWISE_OPERAND_OUT_OF_RANGE, left);
return n;
}
} catch (UnsupportedOperationException ex) {
// left is not a number node, so do not replace, but warn the
// user because they can't be doing anything good
report(NEGATING_A_NON_NUMBER_ERROR, left);
return n;
}
default:
return n;
}
}
/** http://www.ecma-international.org/ecma-262/6.0/#sec-strict-equality-comparison */
private static TernaryValue tryStrictEqualityComparison(Node left, Node right, boolean useTypes) {
// First, try to evaluate based on the general type.
ValueType leftValueType = NodeUtil.getKnownValueType(left);
ValueType rightValueType = NodeUtil.getKnownValueType(right);
if (leftValueType != ValueType.UNDETERMINED && rightValueType != ValueType.UNDETERMINED) {
// Strict equality can only be true for values of the same type.
if (leftValueType != rightValueType) {
return TernaryValue.FALSE;
}
switch (leftValueType) {
case VOID:
case NULL:
return TernaryValue.TRUE;
case NUMBER:
{
if (NodeUtil.isNaN(left)) {
return TernaryValue.FALSE;
}
if (NodeUtil.isNaN(right)) {
return TernaryValue.FALSE;
}
Double lv = NodeUtil.getNumberValue(left, useTypes);
Double rv = NodeUtil.getNumberValue(right, useTypes);
if (lv != null && rv != null) {
return TernaryValue.forBoolean(lv.doubleValue() == rv.doubleValue());
}
break;
}
case STRING:
{
String lv = NodeUtil.getStringValue(left);
String rv = NodeUtil.getStringValue(right);
if (lv != null && rv != null) {
// In JS, browsers parse \v differently. So do not consider strings
// equal if one contains \v.
if (lv.indexOf('\u000B') != -1 || rv.indexOf('\u000B') != -1) {
return TernaryValue.UNKNOWN;
} else {
return lv.equals(rv) ? TernaryValue.TRUE : TernaryValue.FALSE;
}
} else if (left.isTypeOf()
&& right.isTypeOf()
&& left.getFirstChild().isName()
&& right.getFirstChild().isName()
&& left.getFirstChild().getString().equals(right.getFirstChild().getString())) {
// Special case, typeof a == typeof a is always true.
return TernaryValue.TRUE;
}
break;
}
case BOOLEAN:
{
TernaryValue lv = NodeUtil.getPureBooleanValue(left);
TernaryValue rv = NodeUtil.getPureBooleanValue(right);
return lv.and(rv).or(lv.not().and(rv.not()));
}
default: // Symbol and Object cannot be folded in the general case.
return TernaryValue.UNKNOWN;
}
}
// Then, try to evaluate based on the value of the node. There's only one special case:
// Any strict equality comparison against NaN returns false.
if (NodeUtil.isNaN(left) || NodeUtil.isNaN(right)) {
return TernaryValue.FALSE;
}
return TernaryValue.UNKNOWN;
}
