HeaderBag::get() return type extension

extension.neon

@@ -40,3 +40,8 @@ services:
 	-
 		class: PHPStan\Type\Symfony\RequestDynamicReturnTypeExtension
 		tags: [phpstan.broker.dynamicMethodReturnTypeExtension]
+
+	# HeaderBag::get() return type
+	-
+		class: PHPStan\Type\Symfony\HeaderBagDynamicReturnTypeExtension
+		tags: [phpstan.broker.dynamicMethodReturnTypeExtension]

src/Type/Symfony/HeaderBagDynamicReturnTypeExtension.php

@@ -0,0 +1,54 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Symfony;
+
+use PhpParser\Node\Expr\MethodCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+use PHPStan\Type\ArrayType;
+use PHPStan\Type\Constant\ConstantBooleanType;
+use PHPStan\Type\DynamicMethodReturnTypeExtension;
+use PHPStan\Type\IntegerType;
+use PHPStan\Type\NullType;
+use PHPStan\Type\StringType;
+use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
+
+final class HeaderBagDynamicReturnTypeExtension implements DynamicMethodReturnTypeExtension
+{
+
+	public function getClass(): string
+	{
+		return 'Symfony\Component\HttpFoundation\HeaderBag';
+	}
+
+	public function isMethodSupported(MethodReflection $methodReflection): bool
+	{
+		return $methodReflection->getName() === 'get';
+	}
+
+	public function getTypeFromMethodCall(
+		MethodReflection $methodReflection,
+		MethodCall $methodCall,
+		Scope $scope
+	): Type
+	{
+		$firstArgType = isset($methodCall->args[2]) ? $scope->getType($methodCall->args[2]->value) : new ConstantBooleanType(true);
+		$isTrueType = (new ConstantBooleanType(true))->isSuperTypeOf($firstArgType);
+		$isFalseType = (new ConstantBooleanType(false))->isSuperTypeOf($firstArgType);
+		$compareTypes = $isTrueType->compareTo($isFalseType);
+
+		$defaultArgType = isset($methodCall->args[1]) ? $scope->getType($methodCall->args[1]->value) : new NullType();
+
+		if ($compareTypes === $isTrueType) {
+			return TypeCombinator::union($defaultArgType, new StringType());
+		}
+		if ($compareTypes === $isFalseType) {
+			return TypeCombinator::union($defaultArgType, new ArrayType(new IntegerType(), new StringType()));
+		}
+
+		return ParametersAcceptorSelector::selectSingle($methodReflection->getVariants())->getReturnType();
+	}
+
+}

tests/Symfony/NeonTest.php

@@ -40,7 +40,7 @@ public function testExtensionNeon(): void
 		], $container->getParameters());
 
 		self::assertCount(2, $container->findByTag('phpstan.rules.rule'));
-		self::assertCount(4, $container->findByTag('phpstan.broker.dynamicMethodReturnTypeExtension'));
+		self::assertCount(5, $container->findByTag('phpstan.broker.dynamicMethodReturnTypeExtension'));
 		self::assertCount(3, $container->findByTag('phpstan.typeSpecifier.methodTypeSpecifyingExtension'));
 		self::assertInstanceOf(ServiceMap::class, $container->getByType(ServiceMap::class));
 	}

tests/Type/Symfony/HeaderBagDynamicReturnTypeExtensionTest.php

@@ -0,0 +1,37 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Symfony;
+
+use Iterator;
+
+final class HeaderBagDynamicReturnTypeExtensionTest extends ExtensionTestCase
+{
+
+	/**
+	 * @dataProvider getProvider
+	 */
+	public function testGet(string $expression, string $type): void
+	{
+		$this->processFile(
+			__DIR__ . '/header_bag_get.php',
+			$expression,
+			$type,
+			new HeaderBagDynamicReturnTypeExtension()
+		);
+	}
+
+	public function getProvider(): Iterator
+	{
+		yield ['$test1', 'string|null'];
+		yield ['$test2', 'string|null'];
+		yield ['$test3', 'string'];
+		yield ['$test4', 'array<int, string>|string'];
+		yield ['$test5', 'string|null'];
+		yield ['$test6', 'string'];
+		yield ['$test7', 'array<int, string>|string'];
+		yield ['$test8', 'array<int, string>|null'];
+		yield ['$test9', 'array<int, string>|string'];
+		yield ['$test10', 'array<int, string>'];
+	}
+
+}

tests/Type/Symfony/header_bag_get.php

@@ -0,0 +1,18 @@
+<?php declare(strict_types = 1);
+
+$bag = new \Symfony\Component\HttpFoundation\HeaderBag(['foo' => ['bar']]);
+
+$test1 = $bag->get('foo');
+$test2 = $bag->get('foo', null);
+$test3 = $bag->get('foo', 'baz');
+$test4 = $bag->get('foo', ['baz']);
+
+$test5 = $bag->get('foo', null, true);
+$test6 = $bag->get('foo', 'baz', true);
+$test7 = $bag->get('foo', ['baz'], true);
+
+$test8 = $bag->get('foo', null, false);
+$test9 = $bag->get('foo', 'baz', false);
+$test10 = $bag->get('foo', ['baz'], false);
+
+die;