Support for union type as template type bound

src/Rules/Generics/TemplateTypeCheck.php

@@ -11,6 +11,7 @@
 use PHPStan\Type\MixedType;
 use PHPStan\Type\ObjectType;
 use PHPStan\Type\ObjectWithoutClassType;
+use PHPStan\Type\UnionType;
 use PHPStan\Type\VerbosityLevel;
 use function array_key_exists;
 use function array_map;
@@ -106,6 +107,7 @@ public function check(
 				$boundClass === MixedType::class
 				|| $boundClass === ObjectWithoutClassType::class
 				|| $bound instanceof ObjectType
+				|| $bound instanceof UnionType
 			) {
 				continue;
 			}

src/Type/Generic/TemplateBenevolentUnionType.php

@@ -0,0 +1,59 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Generic;
+
+use PHPStan\Type\Type;
+use PHPStan\Type\BenevolentUnionType;
+
+final class TemplateBenevolentUnionType extends BenevolentUnionType implements TemplateType
+{
+
+	use TemplateTypeTrait;
+
+	/**
+	 * @param Type[] $types
+	 */
+	public function __construct(
+		TemplateTypeScope $scope,
+		TemplateTypeStrategy $templateTypeStrategy,
+		TemplateTypeVariance $templateTypeVariance,
+		array $types,
+		string $name
+	)
+	{
+		parent::__construct($types);
+
+		$this->scope = $scope;
+		$this->strategy = $templateTypeStrategy;
+		$this->variance = $templateTypeVariance;
+		$this->name = $name;
+		$this->bound = new BenevolentUnionType($types);
+	}
+
+	public function toArgument(): TemplateType
+	{
+		return new self(
+			$this->scope,
+			new TemplateTypeArgumentStrategy(),
+			$this->variance,
+			$this->getTypes(),
+			$this->name
+		);
+	}
+
+	/**
+	 * @param mixed[] $properties
+	 * @return Type
+	 */
+	public static function __set_state(array $properties): Type
+	{
+		return new self(
+			$properties['scope'],
+			$properties['strategy'],
+			$properties['variance'],
+			$properties['types'],
+			$properties['name']
+		);
+	}
+
+}

src/Type/Generic/TemplateTypeFactory.php

@@ -3,10 +3,12 @@
 namespace PHPStan\Type\Generic;
 
 use PHPStan\PhpDoc\Tag\TemplateTag;
+use PHPStan\Type\BenevolentUnionType;
 use PHPStan\Type\MixedType;
 use PHPStan\Type\ObjectType;
 use PHPStan\Type\ObjectWithoutClassType;
 use PHPStan\Type\Type;
+use PHPStan\Type\UnionType;
 
 final class TemplateTypeFactory
 {
@@ -32,6 +34,16 @@ public static function create(TemplateTypeScope $scope, string $name, ?Type $bou
 			return new TemplateMixedType($scope, $strategy, $variance, $name);
 		}
 
+		if ($bound instanceof UnionType) {
+			if ($boundClass === UnionType::class) {
+				return new TemplateUnionType($scope, $strategy, $variance, $bound->getTypes(), $name);
+			}
+
+			if ($boundClass === BenevolentUnionType::class) {
+				return new TemplateBenevolentUnionType($scope, $strategy, $variance, $bound->getTypes(), $name);
+			}
+		}
+
 		return new TemplateMixedType($scope, $strategy, $variance, $name);
 	}
 

src/Type/Generic/TemplateUnionType.php

@@ -0,0 +1,59 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Generic;
+
+use PHPStan\Type\Type;
+use PHPStan\Type\UnionType;
+
+final class TemplateUnionType extends UnionType implements TemplateType
+{
+
+	use TemplateTypeTrait;
+
+	/**
+	 * @param Type[] $types
+	 */
+	public function __construct(
+		TemplateTypeScope $scope,
+		TemplateTypeStrategy $templateTypeStrategy,
+		TemplateTypeVariance $templateTypeVariance,
+		array $types,
+		string $name
+	)
+	{
+		parent::__construct($types);
+
+		$this->scope = $scope;
+		$this->strategy = $templateTypeStrategy;
+		$this->variance = $templateTypeVariance;
+		$this->name = $name;
+		$this->bound = new UnionType($types);
+	}
+
+	public function toArgument(): TemplateType
+	{
+		return new self(
+			$this->scope,
+			new TemplateTypeArgumentStrategy(),
+			$this->variance,
+			$this->getTypes(),
+			$this->name
+		);
+	}
+
+	/**
+	 * @param mixed[] $properties
+	 * @return Type
+	 */
+	public static function __set_state(array $properties): Type
+	{
+		return new self(
+			$properties['scope'],
+			$properties['strategy'],
+			$properties['variance'],
+			$properties['types'],
+			$properties['name']
+		);
+	}
+
+}

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -10907,6 +10907,12 @@ public function dataBug3321(): array
 		return $this->gatherAssertTypes(__DIR__ . '/data/bug-3321.php');
 	}
 
+	public function dataBug3769(): array
+	{
+		require_once __DIR__ . '/../Rules/Generics/data/bug-3769.php';
+		return $this->gatherAssertTypes(__DIR__ . '/../Rules/Generics/data/bug-3769.php');
+	}
+
 	/**
 	 * @param string $file
 	 * @return array<string, mixed[]>
@@ -11150,6 +11156,7 @@ private function gatherAssertTypes(string $file): array
 	 * @dataProvider dataBug4577
 	 * @dataProvider dataBug4579
 	 * @dataProvider dataBug3321
+	 * @dataProvider dataBug3769
 	 * @param string $assertType
 	 * @param string $file
 	 * @param mixed ...$args

tests/PHPStan/Generics/TemplateTypeFactoryTest.php

@@ -56,7 +56,10 @@ public function dataCreate(): array
 					new StringType(),
 					new IntegerType(),
 				]),
-				new MixedType(),
+				new UnionType([
+					new StringType(),
+					new IntegerType(),
+				]),
 			],
 		];
 	}

tests/PHPStan/Rules/Generics/FunctionTemplateTypeRuleTest.php

@@ -44,4 +44,10 @@ public function testRule(): void
 		]);
 	}
 
+	public function testBug3769(): void
+	{
+		require_once __DIR__ . '/data/bug-3769.php';
+		$this->analyse([__DIR__ . '/data/bug-3769.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Generics/data/bug-3769.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace Bug3769;
+
+use function PHPStan\Analyser\assertType;
+
+/**
+ * @template K of array-key
+ * @param array<K, int> $in
+ * @return array<K, string>
+ */
+function stringValues(array $in): array {
+	assertType('array<K of (int|string) (function Bug3769\stringValues(), argument), int>', $in);
+	return array_map(fn (int $int): string => (string) $int, $in);
+}
+
+/**
+ * @param array<int, int> $foo
+ * @param array<string, int> $bar
+ * @param array<int> $baz
+ */
+function foo(
+	array $foo,
+	array $bar,
+	array $baz
+): void {
+	assertType('array<int, string>', stringValues($foo));
+	assertType('array<string, string>', stringValues($bar));
+	assertType('array<string>', stringValues($baz));
+};
+
+/**
+ * @template T of \stdClass|\Exception
+ * @param T $foo
+ */
+function fooUnion($foo): void {
+	assertType('T of Exception|stdClass (function Bug3769\fooUnion(), argument)', $foo);
+}