Added OffsetType

Closes #27

src/OffsetType.php

@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Typhoon\Type;
+
+/**
+ * @api
+ * @implements Type<mixed>
+ */
+final class OffsetType implements Type
+{
+ public readonly Type $subject;
+
+ public readonly Type $offset;
+
+ /**
+ * @internal
+ * @psalm-internal Typhoon\Type
+ */
+ public function __construct(
+ Type $subject,
+ Type $offset,
+ ) {
+ $this->subject = $subject;
+ $this->offset = $offset;
+ }
+
+ public function accept(TypeVisitor $visitor): mixed
+ {
+ return $visitor->visitOffset($this);
+ }
+}

src/TypeVisitor.php

@@ -151,6 +151,9 @@ public function visitKeyOf(KeyOfType $type): mixed;
  /** @return TReturn */
  public function visitValueOf(ValueOfType $type): mixed;
 
+ /** @return TReturn */
+ public function visitOffset(OffsetType $type): mixed;
+
  /** @return TReturn */
  public function visitTemplate(TemplateType $type): mixed;
 

src/types.php

@@ -334,6 +334,11 @@ public static function valueOf(Type $type): ValueOfType
  return new ValueOfType($type);
  }
 
+ public static function offset(Type $subject, Type $offset): OffsetType
+ {
+ return new OffsetType($subject, $offset);
+ }
+
  /**
  * @template TType
  * @param non-empty-string $name

tests/PsalmTest.php

@@ -64,6 +64,7 @@ public static function extractType(Type $_type): mixed
  #[TestWith([__DIR__ . '/psalm/NumericType.phpt'])]
  #[TestWith([__DIR__ . '/psalm/ObjectShapeType.phpt'])]
  #[TestWith([__DIR__ . '/psalm/ObjectType.phpt'])]
+ #[TestWith([__DIR__ . '/psalm/OffsetType.phpt'])]
  #[TestWith([__DIR__ . '/psalm/ResourceType.phpt'])]
  #[TestWith([__DIR__ . '/psalm/ScalarType.phpt'])]
  #[TestWith([__DIR__ . '/psalm/StaticType.phpt'])]

tests/psalm/OffsetType.phpt

@@ -0,0 +1,9 @@
+--FILE--
+<?php
+
+namespace Typhoon\Type;
+
+$_type = PsalmTest::extractType(new OffsetType(new ListType(), new IntLiteralType(0)));
+/** @psalm-check-type-exact $_type = mixed */
+
+--EXPECT--