[Type] add support for variadic intersection types (#185)

docs/component/type.md

@@ -17,7 +17,7 @@
 - [dict](./../../src/Psl/Type/dict.php#L20)
 - [float](./../../src/Psl/Type/float.php#L10)
 - [int](./../../src/Psl/Type/int.php#L10)
-- [intersection](./../../src/Psl/Type/intersection.php#L20)
+- [intersection](./../../src/Psl/Type/intersection.php#L22)
 - [is_array](./../../src/Psl/Type/is_array.php#L20) ( deprecated )
 - [is_arraykey](./../../src/Psl/Type/is_arraykey.php#L18) ( deprecated )
 - [is_bool](./../../src/Psl/Type/is_bool.php#L20) ( deprecated )

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, $second or one of $rest 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 +1,46 @@
+<?php
+
+declare(strict_types=1);
+
+use Psl\Collection\Map;
+use Psl\Collection\Vector;
+use Psl\Result\ResultInterface;
+use Psl\Type;
+
+/**
+ * @psalm-suppress UnusedParam
+ *
+ * @param Map&ResultInterface&stdClass&Vector $value
+ */
+function takes_valid_intersection($value): void
+{
+}
+
+function test(): void
+{
+    /** @psalm-suppress MissingThrowsDocblock */
+    $old_school_codec = Type\intersection(
+        Type\object(Map::class),
+        Type\intersection(
+            Type\object(ResultInterface::class),
+            Type\intersection(
+                Type\object(stdClass::class),
+                Type\object(Vector::class),
+            )
+        ),
+    );
+
+    /** @psalm-suppress MissingThrowsDocblock */
+    $new_codec = Type\intersection(
+        Type\object(Map::class),
+        Type\object(ResultInterface::class),
+        Type\object(stdClass::class),
+        Type\object(Vector::class),
+    );
+
+    /** @psalm-suppress MissingThrowsDocblock */
+    takes_valid_intersection($old_school_codec->assert('any'));
+
+    /** @psalm-suppress MissingThrowsDocblock */
+    takes_valid_intersection($new_codec->assert('any'));
+}

tests/unit/Type/IntersectionTypeTest.php

@@ -13,7 +13,7 @@ final class IntersectionTypeTest extends TypeTest
 {
     public function testIntersectionLeft(): void
     {
-        $intersection = Type\intersection(Type\array_key(), Type\int());
+        $intersection = Type\intersection(Type\array_key(), Type\int(), Type\positive_int());
 
         static::assertSame(1, $intersection->coerce('1'));
     }
@@ -53,14 +53,36 @@ public function getToStringExamples(): iterable
             'Psl\Collection\IndexAccessInterface&Psl\Collection\CollectionInterface'
         ];
 
-        yield [Type\intersection(
-            Type\object(IndexAccessInterface::class),
-            Type\union(Type\object(CollectionInterface::class), Type\object(Iterator::class))
-        ), 'Psl\Collection\IndexAccessInterface&(Psl\Collection\CollectionInterface|Iterator)'];
+        yield [
+            Type\intersection(
+                Type\object(IndexAccessInterface::class),
+                Type\union(
+                    Type\object(CollectionInterface::class),
+                    Type\object(Iterator::class)
+                )
+            ),
+            'Psl\Collection\IndexAccessInterface&(Psl\Collection\CollectionInterface|Iterator)'
+        ];
 
-        yield [Type\intersection(
-            Type\union(Type\object(CollectionInterface::class), Type\object(Iterator::class)),
-            Type\object(IndexAccessInterface::class)
-        ), '(Psl\Collection\CollectionInterface|Iterator)&Psl\Collection\IndexAccessInterface'];
+        yield [
+            Type\intersection(
+                Type\union(
+                    Type\object(CollectionInterface::class),
+                    Type\object(Iterator::class)
+                ),
+                Type\object(IndexAccessInterface::class)
+            ),
+            '(Psl\Collection\CollectionInterface|Iterator)&Psl\Collection\IndexAccessInterface'
+        ];
+
+        yield [
+            Type\intersection(
+                Type\object(IndexAccessInterface::class),
+                Type\object(CollectionInterface::class),
+                Type\object(Iterator::class),
+                Type\shape(['id' => Type\string()]),
+            ),
+            'Psl\Collection\IndexAccessInterface&Psl\Collection\CollectionInterface&Iterator&array{\'id\': string}'
+        ];
     }
 }