Added failling test

src/Node/ClassPropertiesNode.php

@@ -192,6 +192,10 @@ public function getUninitializedProperties(
 				continue;
 			}
 
+			if ($usageScope->isInAnonymousFunction() && $usageScope->getParentScope() !== null) {
+				$usageScope = $usageScope->getParentScope();
+			}
+
 			$propertyReflection = $usageScope->getPropertyReflection($fetchedOnType, $propertyName);
 			if ($propertyReflection === null) {
 				continue;
@@ -353,6 +357,10 @@ private function getMethodsCalledFromConstructor(
 				continue;
 			}
 
+			if ($callScope->isInAnonymousFunction() && $callScope->getParentScope() !== null) {
+				$callScope = $callScope->getParentScope();
+			}
+
 			$methodName = $methodCallNode->name->toString();
 			if (array_key_exists($methodName, $initializedProperties)) {
 				foreach ($this->getInitializedProperties($callScope, $initializedProperties[$inMethod->getName()] ?? $initialInitializedProperties) as $propertyName => $isInitialized) {

tests/PHPStan/Rules/Properties/MissingReadOnlyPropertyAssignRuleTest.php

@@ -247,6 +247,20 @@ public function testBug9577(): void
 		]);
 	}
 
+	public function testBug10048(): void
+	{
+		if (PHP_VERSION_ID < 80100) {
+			$this->markTestSkipped('Test requires PHP 8.1.');
+		}
+
+		$this->analyse([__DIR__ . '/data/bug-10048.php'], [
+			[
+				'Readonly property Foo::$bar is already assigned',
+				66,
+			],
+		]);
+	}
+
 	public function testAnonymousReadonlyClass(): void
 	{
 		if (PHP_VERSION_ID < 80300) {

tests/PHPStan/Rules/Properties/data/bug-10048.php

@@ -0,0 +1,80 @@
+<?php // lint >= 8.1
+
+namespace Bug10048;
+
+class Foo
+{
+	private readonly string $bar;
+	private readonly \Closure $callback;
+
+	public function __construct()
+	{
+		$this->bar = "hi";
+		$this->useBar();
+		echo $this->bar;
+		$this->callback = function () {
+			$this->useBar();
+		};
+	}
+
+	private function useBar(): void
+	{
+		echo $this->bar;
+	}
+
+	public function useCallback(): void
+	{
+		call_user_func($this->callback);
+	}
+}
+
+function doFoo() {
+	(new Foo())->useCallback();
+}
+
+class Bar
+{
+	private readonly string $bar;
+	private readonly \Closure $callback;
+
+	public function __construct()
+	{
+		$this->bar = "hi";
+
+		$this->callback = function () {
+			$this->useBar();
+		};
+	}
+
+	private function useBar(): void
+	{
+		echo $this->bar;
+	}
+}
+
+
+class CannotModifyAlreadyAssigned
+{
+	private readonly string $bar;
+	private readonly \Closure $callback;
+
+	public function __construct()
+	{
+		$this->bar = "hi";
+
+		$this->callback = function () {
+			$this->bar = "hidiho";
+			$this->useBar();
+		};
+	}
+
+	private function useBar(): void
+	{
+		echo $this->bar;
+	}
+
+	public function useCallback(): void
+	{
+		call_user_func($this->callback);
+	}
+}