Remember narrowed types from the constructor from deep PropertyFetches

Author: staabm

src/Analyser/MutatingScope.php

@@ -356,23 +356,30 @@ public function rememberConstructorScope(): self
 
 	private function isReadonlyPropertyFetchOnThis(PropertyFetch $expr): bool
 	{
-		if (
-			!$expr->name instanceof Node\Identifier
-			|| !$expr->var instanceof Variable
-			|| $expr->var->name !== 'this'
-			|| !$this->phpVersion->supportsReadOnlyProperties()
-		) {
-			return false;
-		}
+		while ($expr instanceof PropertyFetch) {
+			if ($expr->var instanceof Variable) {
+				if (
+					! $expr->name instanceof Node\Identifier
+					|| !is_string($expr->var->name)
+					|| $expr->var->name !== 'this'
+				) {
+					return false;
+				}
+			} elseif (!$expr->var instanceof PropertyFetch) {
+				return false;
+			}
 
-		$propertyReflection = $this->propertyReflectionFinder->findPropertyReflectionFromNode($expr, $this);
-		if ($propertyReflection === null) {
-			return false;
-		}
+			$propertyReflection = $this->propertyReflectionFinder->findPropertyReflectionFromNode($expr, $this);
+			if ($propertyReflection === null) {
+				return false;
+			}
 
-		$nativePropertyReflection = $propertyReflection->getNativeReflection();
-		if ($nativePropertyReflection === null || !$nativePropertyReflection->isReadOnly()) {
-			return false;
+			$nativePropertyReflection = $propertyReflection->getNativeReflection();
+			if ($nativePropertyReflection === null || !$nativePropertyReflection->isReadOnly()) {
+				return false;
+			}
+
+			$expr = $expr->var;
 		}
 
 		return true;

tests/PHPStan/Analyser/nsrt/remember-readonly-constructor-narrowed.php

@@ -2,6 +2,7 @@
 
 namespace RememberReadOnlyConstructor;
 
+use LogicException;
 use function PHPStan\Testing\assertType;
 
 class HelloWorldReadonlyProperty {
@@ -107,3 +108,38 @@ public function doFoo() {
 		assertType('4|10', $this->i);
 	}
 }
+
+class Foo {
+	public readonly int $readonly;
+	public int $writable;
+
+	public function __construct()
+	{
+		$this->readonly = 5;
+		$this->writable = rand(0,1) ? 5 : 10;
+	}
+}
+
+class DeepPropertyFetching {
+	public readonly ?Foo $prop;
+
+	public function __construct() {
+		$this->prop = new Foo();
+		if($this->prop->readonly != 5) {
+			throw new LogicException();
+		}
+		if ($this->prop->writable != 5) {
+			throw new LogicException();
+		}
+
+		assertType(Foo::class, $this->prop);
+		assertType('5', $this->prop->readonly);
+		assertType('5', $this->prop->writable);
+	}
+
+	public function doFoo() {
+		assertType(Foo::class, $this->prop);
+		assertType('5', $this->prop->readonly);
+		assertType('int', $this->prop->writable);
+	}
+}