Feature/variadic intersection type

src/Psl/Type/intersection.php

@@ -7,20 +7,29 @@
 use Psl;
 
 /**
- * @template Tl
- * @template Tr
+ * @template TFirst
+ * @template TSecond
+ * @template TRest
  *
- * @param TypeInterface<Tl> $left_type
- * @param TypeInterface<Tr> $right_type
+ * @param TypeInterface<TFirst> $first
+ * @param TypeInterface<TSecond> $second
+ * @param TypeInterface<TRest> ...$rest
  *
- * @throws Psl\Exception\InvariantViolationException If $left_type, or $right_type is optional.
+ * @throws Psl\Exception\InvariantViolationException If $first, or $second is optional.
  *
- * @return TypeInterface<Tl&Tr>
+ * @return TypeInterface<TFirst&TSecond&TRest>
  */
 function intersection(
-    TypeInterface $left_type,
-    TypeInterface $right_type
+    TypeInterface $first,
+    TypeInterface $second,
+    TypeInterface ...$rest
 ): TypeInterface {
-    /** @var TypeInterface<Tl&Tr> */
-    return new Internal\IntersectionType($left_type, $right_type);
+    $accumulated_type = new Internal\IntersectionType($first, $second);
+
+    foreach ($rest as $type) {
+        $accumulated_type = new Internal\IntersectionType($accumulated_type, $type);
+    }
+
+    /** @var TypeInterface<TFirst&TSecond&TRest> */
+    return $accumulated_type;
 }

tests/static-analysis/Type/intersection.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+use Psl\Collection\Map;
+use Psl\Result\ResultInterface;
+use Psl\Type;
+
+/**
+ * @psalm-suppress UnusedParam
+ *
+ * @param Map&ResultInterface&stdClass $value
+ */
+function takes_valid_intersection($value): void
+{
+}
+
+function test(): void
+{
+    /** @psalm-suppress MissingThrowsDocblock */
+    $old_school_codec = Type\intersection(
+        Type\object(Map::class),
+        Type\intersection(
+            Type\object(ResultInterface::class),
+            Type\object(stdClass::class),
+        ),
+    );
+
+    /** @psalm-suppress MissingThrowsDocblock */
+    $new_codec = Type\intersection(
+        Type\object(Map::class),
+        Type\object(ResultInterface::class),
+        Type\object(stdClass::class),
+    );
+
+    /** @psalm-suppress MissingThrowsDocblock */
+    takes_valid_intersection($old_school_codec->assert('any'));
+
+    /** @psalm-suppress MissingThrowsDocblock */
+    takes_valid_intersection($new_codec->assert('any'));
+}