/**
* Perform an intersection operation between two Types.
*
* If the two types are the same, this will just return that type.
* If the two types are not the same, this will return NULL.
*
* When performed on two UnionTypes, this operation will return another
* Type or UnionType containing the types that were equal from a many-to-many
* typeof() operation or NULL if there are no matches.
*
* UnionType->intersect(NormalType)
* When performed on a UnionType and one normal Type, this operation
* will return the normal type if the UnionType contains the Type, or
* NULL otherwise.
*
* NormalType->intersect(UnionType)
* When performed on a Type and one UnionType, this operation will
* return the Type if the UnionType contains it. NULL otherwise.
*
* Strict operation.
*
* @param Type $a
* @param Type $b
*
* @return Type|null
*/
public static final function intersect(Type $a, Type $b)
{
// Intersecting between $a and $b
$output = [];
$a = $a->getTypes();
$b = $b->getTypes();
// Check all elements of $a
foreach ($a as $x) {
foreach ($b as $y) {
if ($x->typeof($y)) {
$output[] = $x;
}
}
}
// Check all elements of $b
foreach ($b as $x) {
foreach ($a as $y) {
if ($x->typeof($y)) {
$output[] = $x;
}
}
}
// Combine results
return Type::unique(...$output) ?: null;
}
/**
* Check if all types are the same, in which case just return that type.
* Otherwise, create the UnionType and return.
* Also automatically flatten all nested UnionTypes.
*
* @param Type $type Require at least one type
* @param Type|Type[] ...$types
*
* @return UnionType|Type
*/
public static function createIfNotDuplicate(Type $type, Type ...$types)
{
$types = array_merge([$type], $types);
// Flatten nested UnionTypes
$types = Type::flatten($types);
if (array_any($types, function (Type $type, $key, array $collection) {
return $type instanceof UnionType;
})) {
throw new \LogicException("UnionType::flatten() failed to flatten nested UnionTypes.");
}
$types = Type::unique($types);
if (count($types) <= 1) {
return first($types);
}
return new UnionType(array_shift($types), $types);
}