/**
* Unify the two types symmetrically, given that we have already instantiated the type variables
* of interest in {@code t1} and {@code t2}, treating JSType.UNKNOWN as a "hole" to be filled.
*
* @return The unified type, or null if unification fails
*/
static JSType unifyUnknowns(JSType t1, JSType t2) {
if (t1.isUnknown()) {
return t2;
} else if (t2.isUnknown()) {
return t1;
} else if (t1.isTop() && t2.isTop()) {
return TOP;
} else if (t1.isTop() || t2.isTop()) {
return null;
}
int t1Mask = promoteBoolean(t1.mask);
int t2Mask = promoteBoolean(t2.mask);
if (t1Mask != t2Mask || !Objects.equal(t1.typeVar, t2.typeVar)) {
return null;
}
// All scalar types are equal
if ((t1Mask & NON_SCALAR_MASK) == 0) {
return t1;
}
if (t1.objs.size() != t2.objs.size()) {
return null;
}
Set<ObjectType> ununified = Sets.newHashSet(t2.objs);
Set<ObjectType> unifiedObjs = Sets.newHashSet();
for (ObjectType objType1 : t1.objs) {
ObjectType unified = objType1;
boolean hasUnified = false;
for (ObjectType objType2 : t2.objs) {
ObjectType tmp = ObjectType.unifyUnknowns(unified, objType2);
if (tmp != null) {
hasUnified = true;
ununified.remove(objType2);
unified = tmp;
}
}
if (!hasUnified) {
return null;
}
unifiedObjs.add(unified);
}
if (!ununified.isEmpty()) {
return null;
}
return new JSType(t1Mask, null, ImmutableSet.copyOf(unifiedObjs), t1.typeVar);
}
