"Cannot re-assign $this." false-positive

Author: staabm

src/Rules/Variables/InvalidVariableAssignRule.php

@@ -2,12 +2,14 @@
 
 namespace PHPStan\Rules\Variables;
 
+use ArrayAccess;
 use PhpParser\Node;
 use PHPStan\Analyser\Scope;
 use PHPStan\DependencyInjection\RegisteredRule;
 use PHPStan\Node\VariableAssignNode;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\Type\ObjectType;
 use function is_string;
 
 /**
@@ -30,6 +32,13 @@ public function processNode(Node $node, Scope $scope): array
 		}
 
 		if ($variable->name === 'this') {
+			$expr = $node->getAssignedExpr();
+			$type = $scope->getType($expr);
+
+			if ((new ObjectType(ArrayAccess::class))->isSuperTypeOf($type)->yes()) {
+				return [];
+			}
+
 			return [
 				RuleErrorBuilder::message('Cannot re-assign $this.')
 					->identifier('assign.this')

tests/PHPStan/Rules/Variables/InvalidVariableAssignRuleTest.php

@@ -50,6 +50,16 @@ public function testBug3585(): void
 		]);
 	}
 
+	public function testBug14352(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-14352.php'], [
+			[
+				'Cannot re-assign $this.',
+				39,
+			],
+		]);
+	}
+
 	public function testBug14349(): void
 	{
 		$this->analyse([__DIR__ . '/data/bug-14349.php'], [

tests/PHPStan/Rules/Variables/data/bug-14352.php

@@ -0,0 +1,41 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14352;
+
+use ArrayAccess;
+
+class TestArrayAccess implements ArrayAccess
+{
+	public function doFoo(string $key, string $value): void
+	{
+		$this[$key] = $value;
+	}
+
+	public function offsetExists(mixed $offset): bool
+	{
+		// TODO: Implement offsetExists() method.
+	}
+
+	public function offsetGet(mixed $offset): mixed
+	{
+		// TODO: Implement offsetGet() method.
+	}
+
+	public function offsetSet(mixed $offset, mixed $value): void
+	{
+		// TODO: Implement offsetSet() method.
+	}
+
+	public function offsetUnset(mixed $offset): void
+	{
+		// TODO: Implement offsetUnset() method.
+	}
+}
+
+final class TestPlain
+{
+	public function doFoo(string $key, string $value): void
+	{
+		$this[$key] = $value;
+	}
+}