Report a class declared in a method instead of crashing

Makefile

@@ -31,6 +31,7 @@ lint:
 		--exclude tests/PHPStan/Rules/Classes/data/implements-error.php \
 		--exclude tests/PHPStan/Rules/Classes/data/interface-extends-error.php \
 		--exclude tests/PHPStan/Rules/Classes/data/trait-use-error.php \
+		--exclude tests/PHPStan/Rules/Classes/data/nested-class-declaration.php \
 		--exclude tests/PHPStan/Rules/Methods/data/method-in-enum-without-body.php \
 		--exclude tests/PHPStan/Rules/Properties/data/default-value-for-native-property-type.php \
 		--exclude tests/PHPStan/Rules/Arrays/data/empty-array-item.php \

src/Analyser/StmtHandler/ClassLikeHandler.php

@@ -96,7 +96,9 @@ public function processStmt(
 		$name = $stmt->namespacedName ?? $stmt->name;
 		$scope = $scope->invalidateExistenceCheckExpressions($existenceCheckFunctionNames, $name instanceof Name ? $name->toString() : null);
 
-		if (!$context->isTopLevel()) {
+		// PHP does not compile a class declared inside another class (NestedClassDeclarationRule),
+		// and entering it here would replace the class the scope is already in
+		if (!$context->isTopLevel() || (isset($stmt->namespacedName) && $scope->isInClass())) {
 			return new InternalStatementResult($scope, hasYield: false, isAlwaysTerminating: false, exitPoints: [], throwPoints: [], impurePoints: [], dependencies: $declarationDependencies);
 		}
 		if (isset($stmt->namespacedName)) {

src/Rules/Classes/NestedClassDeclarationRule.php

@@ -0,0 +1,55 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Classes;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\DependencyInjection\RegisteredRule;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use function sprintf;
+
+/**
+ * PHP does not compile a class, interface, trait or enum declared inside a class: a method body,
+ * or a closure in one. The analysis skips such a declaration, and this rule reports it.
+ *
+ * @implements Rule<Node\Stmt\ClassLike>
+ */
+#[RegisteredRule(level: 0)]
+final class NestedClassDeclarationRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return Node\Stmt\ClassLike::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if (!isset($node->namespacedName) || !$scope->isInClass()) {
+			return [];
+		}
+
+		if ($node instanceof Node\Stmt\Interface_) {
+			$kind = 'Interface';
+		} elseif ($node instanceof Node\Stmt\Trait_) {
+			$kind = 'Trait';
+		} elseif ($node instanceof Node\Stmt\Enum_) {
+			$kind = 'Enum';
+		} else {
+			$kind = 'Class';
+		}
+
+		return [
+			RuleErrorBuilder::message(sprintf(
+				'%s %s is declared in a method, but class declarations may not be nested.',
+				$kind,
+				$node->namespacedName->toString(),
+			))
+				->identifier('class.inner')
+				->nonIgnorable()
+				->build(),
+		];
+	}
+
+}

src/Turbo/TurboExtensionEnabler.php

@@ -33,7 +33,7 @@
 final class TurboExtensionEnabler
 {
 
-	public const EXPECTED_EXTENSION_VERSION = '28c29b8';
+	public const EXPECTED_EXTENSION_VERSION = '7d92742';
 
 	private static bool $active = false;
 

tests/PHPStan/Rules/Classes/NestedClassDeclarationRuleTest.php

@@ -0,0 +1,51 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Classes;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+use PHPUnit\Framework\Attributes\RequiresPhp;
+
+/**
+ * @extends RuleTestCase<NestedClassDeclarationRule>
+ */
+class NestedClassDeclarationRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new NestedClassDeclarationRule();
+	}
+
+	#[RequiresPhp('>= 8.1.0')]
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/nested-class-declaration.php'], [
+			[
+				'Class NestedClassDeclaration\NestedClass is declared in a method, but class declarations may not be nested.',
+				10,
+			],
+			[
+				'Interface NestedClassDeclaration\NestedInterface is declared in a method, but class declarations may not be nested.',
+				14,
+			],
+			[
+				'Trait NestedClassDeclaration\NestedTrait is declared in a method, but class declarations may not be nested.',
+				18,
+			],
+			[
+				'Enum NestedClassDeclaration\NestedEnum is declared in a method, but class declarations may not be nested.',
+				22,
+			],
+			[
+				'Class NestedClassDeclaration\InClosure is declared in a method, but class declarations may not be nested.',
+				27,
+			],
+			[
+				'Class NestedClassDeclaration\InTraitMethod is declared in a method, but class declarations may not be nested.',
+				62,
+			],
+		]);
+	}
+
+}

tests/PHPStan/Rules/Classes/data/nested-class-declaration.php

@@ -0,0 +1,74 @@
+<?php // lint >= 8.1
+
+namespace NestedClassDeclaration;
+
+class Foo
+{
+
+	public function doFoo(): void
+	{
+		class NestedClass
+		{
+		}
+
+		interface NestedInterface
+		{
+		}
+
+		trait NestedTrait
+		{
+		}
+
+		enum NestedEnum
+		{
+		}
+
+		$f = function (): void {
+			class InClosure
+			{
+			}
+		};
+
+		$anonymous = new class {
+
+			public function doBar(): int
+			{
+				return 1;
+			}
+
+		};
+	}
+
+}
+
+function doBaz(): void
+{
+	class InFunction
+	{
+	}
+
+	$f = function (): void {
+		class InClosureInFunction
+		{
+		}
+	};
+}
+
+trait DeclaresInMethod
+{
+
+	public function doTrait(): void
+	{
+		class InTraitMethod
+		{
+		}
+	}
+
+}
+
+class UsesTheTrait
+{
+
+	use DeclaresInMethod;
+
+}

turbo-ext/src/ClassLikeHandler.cpp

@@ -282,6 +282,15 @@ class ClassLikeHandler
 		zv::Val classReflection;
 		zval *namespacedName = rawNodeProperty(pt_clh_namespaced_name_site, stmt, PT_LC("namespacedName"));
 		if (namespacedName != NULL) ZVAL_DEREF(namespacedName);
+		/* PHP does not compile a class declared inside another class, and entering it would
+		 * replace the class the scope is already in - the PHP twin's isset() && isInClass() */
+		if (namespacedName != NULL && Z_TYPE_P(namespacedName) != IS_UNDEF && Z_TYPE_P(namespacedName) != IS_NULL) {
+			bool isInClass;
+			if (UNEXPECTED(!pt_scope_is_in_class(Z_OBJ_P(resultScope), isInClass))) return zv::Val();
+			if (isInClass) {
+				return pt_internal_statement_result_new(resultScope, false, false, &emptyArray, &emptyArray, &emptyArray, NULL, NULL, -1, declarationDependencies.raw());
+			}
+		}
 		if (namespacedName != NULL && Z_TYPE_P(namespacedName) != IS_UNDEF && Z_TYPE_P(namespacedName) != IS_NULL) {
 			if (UNEXPECTED(Z_TYPE_P(namespacedName) != IS_OBJECT)) {
 				memberCallOnNonObject("toString", namespacedName);