Fixed __toString() return type combining with phpDoc type

Author: ondrejmirtes

src/Reflection/Php/PhpMethodFromParserNodeReflection.php

@@ -54,6 +54,34 @@ public function __construct(
 		bool $isFinal
 	)
 	{
+		$name = strtolower($classMethod->name->name);
+		if (
+			$name === '__construct'
+			|| $name === '__destruct'
+			|| $name === '__unset'
+			|| $name === '__wakeup'
+			|| $name === '__clone'
+		) {
+			$realReturnTypePresent = true;
+			$realReturnType = new VoidType();
+		}
+		if ($name === '__tostring') {
+			$realReturnTypePresent = true;
+			$realReturnType = new StringType();
+		}
+		if ($name === '__isset') {
+			$realReturnTypePresent = true;
+			$realReturnType = new BooleanType();
+		}
+		if ($name === '__sleep') {
+			$realReturnTypePresent = true;
+			$realReturnType = new ArrayType(new IntegerType(), new StringType());
+		}
+		if ($name === '__set_state') {
+			$realReturnTypePresent = true;
+			$realReturnType = new ObjectWithoutClassType();
+		}
+
 		parent::__construct(
 			$classMethod,
 			$templateTypeMap,
@@ -108,34 +136,6 @@ public function isPublic(): bool
 		return $this->getClassMethod()->isPublic();
 	}
 
-	protected function getReturnType(): Type
-	{
-		$name = strtolower($this->getName());
-		if (
-			$name === '__construct'
-			|| $name === '__destruct'
-			|| $name === '__unset'
-			|| $name === '__wakeup'
-			|| $name === '__clone'
-		) {
-			return new VoidType();
-		}
-		if ($name === '__tostring') {
-			return new StringType();
-		}
-		if ($name === '__isset') {
-			return new BooleanType();
-		}
-		if ($name === '__sleep') {
-			return new ArrayType(new IntegerType(), new StringType());
-		}
-		if ($name === '__set_state') {
-			return new ObjectWithoutClassType();
-		}
-
-		return parent::getReturnType();
-	}
-
 	public function getDocComment(): ?string
 	{
 		return null;

src/Reflection/Php/PhpMethodReflection.php

@@ -377,19 +377,19 @@ private function getReturnType(): Type
 				|| $name === '__wakeup'
 				|| $name === '__clone'
 			) {
-				return $this->returnType = new VoidType();
+				return $this->returnType = TypehintHelper::decideType(new VoidType(), $this->phpDocReturnType);
 			}
 			if ($name === '__tostring') {
-				return $this->returnType = new StringType();
+				return $this->returnType = TypehintHelper::decideType(new StringType(), $this->phpDocReturnType);
 			}
 			if ($name === '__isset') {
-				return $this->returnType = new BooleanType();
+				return $this->returnType = TypehintHelper::decideType(new BooleanType(), $this->phpDocReturnType);
 			}
 			if ($name === '__sleep') {
-				return $this->returnType = new ArrayType(new IntegerType(), new StringType());
+				return $this->returnType = TypehintHelper::decideType(new ArrayType(new IntegerType(), new StringType()), $this->phpDocReturnType);
 			}
 			if ($name === '__set_state') {
-				return $this->returnType = new ObjectWithoutClassType();
+				return $this->returnType = TypehintHelper::decideType(new ObjectWithoutClassType(), $this->phpDocReturnType);
 			}
 
 			$this->returnType = TypehintHelper::decideTypeFromReflection(

src/Type/ObjectType.php

@@ -328,7 +328,7 @@ public function toString(): Type
 		}
 
 		if ($classReflection->hasNativeMethod('__toString')) {
-			return new StringType();
+			return ParametersAcceptorSelector::selectSingle($classReflection->getNativeMethod('__toString')->getVariants())->getReturnType();
 		}
 
 		return new ErrorType();

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -9848,6 +9848,11 @@ public function dataConstExprPhpDocType(): array
 		return $this->gatherAssertTypes(__DIR__ . '/data/const-expr-phpdoc-type.php');
 	}
 
+	public function dataBug3226(): array
+	{
+		return $this->gatherAssertTypes(__DIR__ . '/data/bug-3226.php');
+	}
+
 	/**
 	 * @dataProvider dataBug2574
 	 * @dataProvider dataBug2577
@@ -9887,6 +9892,7 @@ public function dataConstExprPhpDocType(): array
 	 * @dataProvider dataArrayShapeKeysStrings
 	 * @dataProvider dataBug1216
 	 * @dataProvider dataConstExprPhpDocType
+	 * @dataProvider dataBug3226
 	 * @param ConstantStringType $expectedType
 	 * @param Type $actualType
 	 */

tests/PHPStan/Analyser/data/bug-3226.php

@@ -0,0 +1,72 @@
+<?php
+
+namespace Bug3226;
+
+use function PHPStan\Analyser\assertType;
+
+class Foo
+{
+	/**
+	 * @var class-string
+	 */
+	private $class;
+
+	/**
+	 * @param class-string $class
+	 */
+	public function __construct(string $class)
+	{
+		$this->class = $class;
+	}
+
+	/**
+	 * @return class-string
+	 */
+	public function __toString(): string
+	{
+		return $this->class;
+	}
+}
+
+function (Foo $foo): void {
+	assertType('class-string', $foo->__toString());
+	assertType('class-string', (string) $foo);
+};
+
+/**
+ * @template T
+ */
+class Bar
+{
+	/**
+	 * @var class-string<T>
+	 */
+	private $class;
+
+	/**
+	 * @param class-string<T> $class
+	 */
+	public function __construct(string $class)
+	{
+		$this->class = $class;
+	}
+
+	/**
+	 * @return class-string<T>
+	 */
+	public function __toString(): string
+	{
+		return $this->class;
+	}
+}
+
+function (Bar $bar): void {
+	assertType('class-string<mixed>', $bar->__toString());
+	assertType('class-string<mixed>', (string) $bar);
+};
+
+function (): void {
+	$bar = new Bar(\Exception::class);
+	assertType('class-string<Exception>', $bar->__toString());
+	assertType('class-string<Exception>', (string) $bar);
+};