Fix #13563: Closure / Arrow functions type difference when an array is reset

src/Analyser/MutatingScope.php

@@ -2829,6 +2829,33 @@
 		return $filteredExpressionTypes;
 	}
 
+	/**
+	 * @param array<string, ExpressionTypeHolder> $expressionTypes
+	 * @return array<string, ExpressionTypeHolder>
+	 */
+	private function invalidateNonReadonlyPropertyFetches(array $expressionTypes): array
+	{
+		$filteredExpressionTypes = [];
+		$nodeFinder = new NodeFinder();
+		foreach ($expressionTypes as $exprString => $expressionType) {
+			$expr = $expressionType->getExpr();
+
+			$propertyFetch = $nodeFinder->findFirst(
+				[$expr],
+				fn ($node) => $node instanceof PropertyFetch
+					&& $node->var instanceof Variable
+					&& $node->var->name === 'this'
+					&& !$this->isReadonlyPropertyFetch($node, true),
+			);
+			if ($propertyFetch !== null) {
+				continue;
+			}
+
+			$filteredExpressionTypes[$exprString] = $expressionType;
+		}
+		return $filteredExpressionTypes;
+	}
+
 	/**
 	 * @api
 	 * @param ParameterReflection[]|null $callableParameters
@@ -2901,13 +2928,20 @@
 			$arrowFunctionScope = $arrowFunctionScope->invalidateExpression(new Variable('this'));
 		}
 
+		$expressionTypes = $this->invalidateStaticExpressions($arrowFunctionScope->expressionTypes);
+		$nativeExpressionTypes = $arrowFunctionScope->nativeExpressionTypes;
+		if (!$arrowFunction->static && $this->hasVariableType('this')->yes()) {
+			$expressionTypes = $this->invalidateNonReadonlyPropertyFetches($expressionTypes);
+			$nativeExpressionTypes = $this->invalidateNonReadonlyPropertyFetches($nativeExpressionTypes);
+		}
+
 		return $this->scopeFactory->create(
 			$arrowFunctionScope->context,
 			$this->isDeclareStrictTypes(),
 			$arrowFunctionScope->getFunction(),
 			$arrowFunctionScope->getNamespace(),
-			$this->invalidateStaticExpressions($arrowFunctionScope->expressionTypes),
-			$arrowFunctionScope->nativeExpressionTypes,
+			$expressionTypes,
+			$nativeExpressionTypes,
 			$arrowFunctionScope->conditionalExpressions,
 			$arrowFunctionScope->inClosureBindScopeClasses,
 			new ClosureType(),

src/Type/Generic/TemplateTypeTrait.php

@@ -72,8 +72,9 @@ public function describe(VerbosityLevel $level): string
 				$boundDescription = sprintf(' of %s', $this->bound->describe($level));
 			}
 			$defaultDescription = '';
-			if ($this->default !== null) {
-				$recursionGuard = RecursionGuard::runOnObjectIdentity($this->default, fn () => $this->default->describe($level));
+			$default = $this->default;
+			if ($default !== null) {
+				$recursionGuard = RecursionGuard::runOnObjectIdentity($default, fn () => $default->describe($level));
 				if (!$recursionGuard instanceof ErrorType) {
 					$defaultDescription .= sprintf(' = %s', $recursionGuard);
 				}

tests/PHPStan/Analyser/nsrt/bug-13563.php

@@ -0,0 +1,55 @@
+<?php declare(strict_types=1);
+
+namespace Bug13563;
+
+use function PHPStan\Testing\assertType;
+
+class Invoker
+{
+	/**
+	 * @var array<string, \Closure>
+	 */
+	private array $callbacks = [];
+
+	public function willReturnCallback(string $method, callable $callback): void
+	{
+		$this->callbacks[$method] = \Closure::fromCallable($callback);
+	}
+}
+
+class MyTest
+{
+	/**
+	 * @var array<int, \DateTime>
+	 */
+	private array $dates = [];
+
+	/**
+	 * @var array<int, \DateTime>
+	 */
+	private array $propNotCleared = [];
+
+	public function setUp(): void
+	{
+		$invoker = new Invoker();
+		$this->dates = [];
+
+		// Arrow function should see the PHPDoc type, not the narrowed array{} from parent scope
+		$invoker->willReturnCallback('get1', fn (int $id) => assertType('array<int, DateTime>', $this->dates));
+
+		// Closure sees the PHPDoc type - this works correctly
+		$invoker->willReturnCallback('get2', function (int $id) {
+			assertType('array<int, DateTime>', $this->dates);
+		});
+
+		// Property not cleared - both should see PHPDoc type
+		$invoker->willReturnCallback('get3', fn (int $id) => assertType('array<int, DateTime>', $this->propNotCleared));
+
+		$invoker->willReturnCallback('get4', function (int $id) {
+			assertType('array<int, DateTime>', $this->propNotCleared);
+		});
+
+		// Arrow function accessing property via array dim fetch - should also use PHPDoc type
+		$invoker->willReturnCallback('get5', fn (int $id): ?\DateTime => $this->dates[$id] ?? null);
+	}
+}