/** http://www.ecma-international.org/ecma-262/6.0/#sec-abstract-relational-comparison */
private static TernaryValue tryAbstractRelationalComparison(
Node left, Node right, boolean useTypes, boolean willNegate) {
// 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) {
if (leftValueType == ValueType.STRING && rightValueType == ValueType.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 compare strings if one contains \v.
if (lv.indexOf('\u000B') != -1 || rv.indexOf('\u000B') != -1) {
return TernaryValue.UNKNOWN;
} else {
return TernaryValue.forBoolean(lv.compareTo(rv) < 0);
}
} 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 false.
return TernaryValue.FALSE;
}
}
}
// Then, try to evaluate based on the value of the node. Try comparing as numbers.
Double lv = NodeUtil.getNumberValue(left, useTypes);
Double rv = NodeUtil.getNumberValue(right, useTypes);
if (lv == null || rv == null) {
// Special case: `x < x` is always false.
//
// TODO(moz): If we knew the named value wouldn't be NaN, it would be nice to handle
// LE and GE. We should use type information if available here.
if (!willNegate && left.isName() && right.isName()) {
if (left.getString().equals(right.getString())) {
return TernaryValue.FALSE;
}
}
return TernaryValue.UNKNOWN;
}
if (Double.isNaN(lv) || Double.isNaN(rv)) {
return TernaryValue.forBoolean(willNegate);
} else {
return TernaryValue.forBoolean(lv.doubleValue() < rv.doubleValue());
}
}
/** 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;
}