JSType getGreatestSubtypeHelper(JSType that) {
if (that.isRecordType()) {
RecordType thatRecord = that.toMaybeRecordType();
RecordTypeBuilder builder = new RecordTypeBuilder(registry);
builder.setSynthesized(true);
// The greatest subtype consists of those *unique* properties of both
// record types. If any property conflicts, then the NO_TYPE type
// is returned.
for (String property : getOwnPropertyNames()) {
if (thatRecord.hasProperty(property)
&& !thatRecord.getPropertyType(property).isInvariant(getPropertyType(property))) {
return registry.getNativeObjectType(JSTypeNative.NO_TYPE);
}
builder.addProperty(property, getPropertyType(property), getPropertyNode(property));
}
for (String property : thatRecord.getOwnPropertyNames()) {
if (!hasProperty(property)) {
builder.addProperty(
property, thatRecord.getPropertyType(property), thatRecord.getPropertyNode(property));
}
}
return builder.build();
}
JSType greatestSubtype = registry.getNativeType(JSTypeNative.NO_OBJECT_TYPE);
JSType thatRestrictedToObj =
registry.getNativeType(JSTypeNative.OBJECT_TYPE).getGreatestSubtype(that);
if (!thatRestrictedToObj.isEmptyType()) {
// In this branch, the other type is some object type. We find
// the greatest subtype with the following algorithm:
// 1) For each property "x" of this record type, take the union
// of all classes with a property "x" with a compatible property type.
// and which are a subtype of {@code that}.
// 2) Take the intersection of all of these unions.
for (String propName : getOwnPropertyNames()) {
JSType propType = getPropertyType(propName);
UnionTypeBuilder builder = new UnionTypeBuilder(registry);
for (ObjectType alt : registry.getEachReferenceTypeWithProperty(propName)) {
JSType altPropType = alt.getPropertyType(propName);
if (altPropType != null
&& !alt.isEquivalentTo(this)
&& alt.isSubtype(that)
&& propType.isInvariant(altPropType)) {
builder.addAlternate(alt);
}
}
greatestSubtype = greatestSubtype.getLeastSupertype(builder.build());
}
}
return greatestSubtype;
}
@Override
boolean defineProperty(String name, JSType type, boolean inferred, Node propertyNode) {
if ("prototype".equals(name)) {
ObjectType objType = type.toObjectType();
if (objType != null) {
if (prototypeSlot != null && objType.isEquivalentTo(prototypeSlot.getType())) {
return true;
}
setPrototypeBasedOn(objType, propertyNode);
return true;
} else {
return false;
}
}
return super.defineProperty(name, type, inferred, propertyNode);
}