// When joining w/ TOP or UNKNOWN, avoid setting more fields on them, eg, obj.
public static JSType join(JSType lhs, JSType rhs) {
if (lhs.isTop() || rhs.isTop()) {
return TOP;
} else if (lhs.isUnknown() || rhs.isUnknown()) {
return UNKNOWN;
} else if (lhs.isBottom()) {
return rhs;
} else if (rhs.isBottom()) {
return lhs;
}
if (lhs.typeVar != null && rhs.typeVar != null && !lhs.typeVar.equals(rhs.typeVar)) {
// For now return ? when joining two type vars. This is probably uncommon.
return UNKNOWN;
}
return new JSType(
lhs.mask | rhs.mask,
joinLocs(lhs.location, rhs.location),
ObjectType.joinSets(lhs.objs, rhs.objs),
lhs.typeVar != null ? lhs.typeVar : rhs.typeVar);
}
