Readonly properties cannot be invalidated

src/Analyser/MutatingScope.php

@@ -3827,7 +3827,19 @@ public function invalidateExpression(Expr $expressionToInvalidate, bool $require
 			if (!$expr instanceof Node\Stmt\Expression) {
 				throw new ShouldNotHappenException();
 			}
-			$found = $nodeFinder->findFirst([$expr->expr], function (Node $node) use ($expressionToInvalidateClass, $exprStringToInvalidate): bool {
+
+			$exprExpr = $expr->expr;
+			if ($exprExpr instanceof PropertyFetch) {
+				$propertyReflection = $this->propertyReflectionFinder->findPropertyReflectionFromNode($exprExpr, $this);
+				if ($propertyReflection !== null) {
+					$nativePropertyReflection = $propertyReflection->getNativeReflection();
+					if ($nativePropertyReflection !== null && $nativePropertyReflection->isReadOnly()) {
+						continue;
+					}
+				}
+			}
+
+			$found = $nodeFinder->findFirst([$exprExpr], function (Node $node) use ($expressionToInvalidateClass, $exprStringToInvalidate): bool {
 				if (!$node instanceof $expressionToInvalidateClass) {
 					return false;
 				}

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -602,6 +602,11 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-2806.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-5328.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-3044.php');
+
+		if (PHP_VERSION_ID >= 80100) {
+			yield from $this->gatherAssertTypes(__DIR__ . '/data/invalidate-readonly-properties.php');
+		}
+
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/weird-array_key_exists-issue.php');
 	}
 

tests/PHPStan/Analyser/data/invalidate-readonly-properties.php

@@ -0,0 +1,31 @@
+<?php // lint >= 8.1
+
+namespace InvalidateReadonlyProperties;
+
+use function PHPStan\Testing\assertType;
+
+class Foo
+{
+
+	private readonly int $foo;
+
+	public function __construct(int $foo)
+	{
+		$this->foo = $foo;
+	}
+
+	public function doFoo(): void
+	{
+		if ($this->foo === 1) {
+			assertType('1', $this->foo);
+			$this->doBar();
+			assertType('1', $this->foo);
+		}
+	}
+
+	public function doBar(): void
+	{
+
+	}
+
+}