Added VarianceAwareType

src/TypeVisitor.php

@@ -127,6 +127,9 @@ public function visitUnion(UnionType $type): mixed;
     /** @return TReturn */
     public function visitValueOf(ValueOfType $type): mixed;
 
+    /** @return TReturn */
+    public function visitVarianceAware(VarianceAwareType $type): mixed;
+
     /** @return TReturn */
     public function visitVoid(VoidType $type): mixed;
 }

src/Variance.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Typhoon\Type;
+
+/**
+ * @api
+ * @psalm-immutable
+ */
+enum Variance
+{
+    case INVARIANT;
+    case COVARIANT;
+    case CONTRAVARIANT;
+    case BIVARIANT;
+}

src/VarianceAwareType.php

@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Typhoon\Type;
+
+/**
+ * @api
+ * @template-covariant TType
+ * @implements Type<TType>
+ */
+final class VarianceAwareType implements Type
+{
+    /**
+     * @var Type<TType>
+     */
+    public readonly Type $type;
+
+    public readonly Variance $variance;
+
+    /**
+     * @internal
+     * @psalm-internal Typhoon\Type
+     * @param Type<TType> $type
+     */
+    public function __construct(
+        Type $type,
+        Variance $variance,
+    ) {
+        $this->type = $type;
+        $this->variance = $variance;
+    }
+
+    public function accept(TypeVisitor $visitor): mixed
+    {
+        return $visitor->visitVarianceAware($this);
+    }
+}

src/types.php

@@ -420,6 +420,16 @@ public static function valueOf(Type $type): ValueOfType
     {
         return new ValueOfType($type);
     }
+
+    /**
+     * @template TType
+     * @param Type<TType> $type
+     * @return VarianceAwareType<TType>
+     */
+    public static function varianceAware(Type $type, Variance $variance): VarianceAwareType
+    {
+        return new VarianceAwareType($type, $variance);
+    }
 }
 
 /**

tests/PsalmTest.php

@@ -64,6 +64,7 @@ public static function extractType(Type $_type): mixed
     #[TestWith([__DIR__ . '/psalm/types.phpt'])]
     #[TestWith([__DIR__ . '/psalm/UnionType.phpt'])]
     #[TestWith([__DIR__ . '/psalm/ValueOfType.phpt'])]
+    #[TestWith([__DIR__ . '/psalm/VarianceAwareType.phpt'])]
     #[TestWith([__DIR__ . '/psalm/VoidType.phpt'])]
     public function testPhptFiles(string $phptFile): void
     {

tests/psalm/VarianceAwareType.phpt

@@ -0,0 +1,9 @@
+--FILE--
+<?php
+
+namespace Typhoon\Type;
+
+$_type = PsalmTest::extractType(new VarianceAwareType(StringType::type, Variance::INVARIANT));
+/** @psalm-check-type-exact $_type = string */
+
+--EXPECT--