Get the right component type with array access

Author: ondrejmirtes

composer.json

@@ -11,7 +11,7 @@
 	},
 	"require": {
 		"php": "~7.1",
-		"phpstan/phpstan": "^0.10",
+		"phpstan/phpstan": "^0.10.2",
 		"nikic/php-parser": "^4.0"
 	},
 	"require-dev": {

extension.neon

@@ -28,6 +28,11 @@ services:
 			- phpstan.broker.propertiesClassReflectionExtension
 			- phpstan.broker.methodsClassReflectionExtension
 
+	-
+		class: PHPStan\Type\Nette\ComponentModelArrayAccessDynamicReturnTypeExtension
+		tags:
+			- phpstan.broker.dynamicMethodReturnTypeExtension
+
 	-
 		class: PHPStan\Type\Nette\ComponentModelDynamicReturnTypeExtension
 		tags:

src/Type/Nette/ComponentModelArrayAccessDynamicReturnTypeExtension.php

@@ -0,0 +1,59 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Nette;
+
+use PhpParser\Node\Expr\MethodCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+use PHPStan\Type\Constant\ConstantStringType;
+use PHPStan\Type\DynamicMethodReturnTypeExtension;
+use PHPStan\Type\MixedType;
+use PHPStan\Type\Type;
+
+class ComponentModelArrayAccessDynamicReturnTypeExtension implements DynamicMethodReturnTypeExtension
+{
+
+	public function getClass(): string
+	{
+		return 'Nette\Application\UI\Component';
+	}
+
+	public function isMethodSupported(
+		MethodReflection $methodReflection
+	): bool
+	{
+		return $methodReflection->getName() === 'offsetGet';
+	}
+
+	public function getTypeFromMethodCall(
+		MethodReflection $methodReflection,
+		MethodCall $methodCall,
+		Scope $scope
+	): Type
+	{
+		$calledOnType = $scope->getType($methodCall->var);
+		$mixedType = new MixedType();
+		$args = $methodCall->args;
+		if (count($args) !== 1) {
+			return $mixedType;
+		}
+
+		$argType = $scope->getType($args[0]->value);
+		if (!$argType instanceof ConstantStringType) {
+			return $mixedType;
+		}
+
+		$componentName = $argType->getValue();
+
+		$methodName = sprintf('createComponent%s', ucfirst($componentName));
+		if (!$calledOnType->hasMethod($methodName)) {
+			return $mixedType;
+		}
+
+		$method = $calledOnType->getMethod($methodName, $scope);
+
+		return ParametersAcceptorSelector::selectSingle($method->getVariants())->getReturnType();
+	}
+
+}