implemented a rule to detect overwriting parent scope vars in for loop init

Author: dktapps

rules.neon

@@ -60,3 +60,10 @@ services:
 			universalObjectCratesClasses: %universalObjectCratesClasses%
 		tags:
 			- phpstan.rules.rule
+
+	-
+		class: PHPStan\Rules\ForLoop\OverwriteVariablesWithForLoopInitRule
+
+conditionalTags:
+	PHPStan\Rules\ForLoop\OverwriteVariablesWithForLoopInitRule:
+		phpstan.rules.rule: %featureToggles.bleedingEdge%

src/Rules/ForLoop/OverwriteVariablesWithForLoopInitRule.php

@@ -0,0 +1,78 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\ForLoop;
+
+use PhpParser\Node;
+use PhpParser\Node\Expr;
+use PhpParser\Node\Expr\Assign;
+use PhpParser\Node\Stmt\For_;
+use PHPStan\Analyser\Scope;
+use PHPStan\Rules\Rule;
+
+/**
+ * @implements Rule<For_>
+ */
+class OverwriteVariablesWithForLoopInitRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return For_::class;
+	}
+
+	/**
+	 * @param For_ $node
+	 * @param Scope $scope
+	 * @return string[]
+	 */
+	public function processNode(Node $node, Scope $scope): array
+	{
+		$errors = [];
+		foreach ($node->init as $expr) {
+			if (!($expr instanceof Assign)) {
+				continue;
+			}
+
+			foreach ($this->checkValueVar($scope, $expr->var) as $error) {
+				$errors[] = $error;
+			}
+		}
+
+		return $errors;
+	}
+
+	/**
+	 * @param Scope $scope
+	 * @param Expr $expr
+	 * @return string[]
+	 */
+	private function checkValueVar(Scope $scope, Expr $expr): array
+	{
+		$errors = [];
+		if (
+			$expr instanceof Node\Expr\Variable
+			&& is_string($expr->name)
+			&& $scope->hasVariableType($expr->name)->yes()
+		) {
+			$errors[] = sprintf('For loop initial assignment overwrites variable $%s.', $expr->name);
+		}
+
+		if (
+			$expr instanceof Node\Expr\List_
+			|| $expr instanceof Node\Expr\Array_
+		) {
+			foreach ($expr->items as $item) {
+				if ($item === null) {
+					continue;
+				}
+
+				foreach ($this->checkValueVar($scope, $item->value) as $error) {
+					$errors[] = $error;
+				}
+			}
+		}
+
+		return $errors;
+	}
+
+}

tests/Rules/ForLoop/OverwriteVariablesWithForLoopInitRuleTest.php

@@ -0,0 +1,65 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\ForLoop;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @template-extends RuleTestCase<OverwriteVariablesWithForLoopInitRule>
+ */
+class OverwriteVariablesWithForLoopInitRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new OverwriteVariablesWithForLoopInitRule();
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/data.php'], [
+			[
+				'For loop initial assignment overwrites variable $i.',
+				9,
+			],
+			[
+				'For loop initial assignment overwrites variable $i.',
+				20,
+			],
+			[
+				'For loop initial assignment overwrites variable $j.',
+				20,
+			],
+			[
+				'For loop initial assignment overwrites variable $i.',
+				24,
+			],
+			[
+				'For loop initial assignment overwrites variable $i.',
+				35,
+			],
+			[
+				'For loop initial assignment overwrites variable $j.',
+				35,
+			],
+			[
+				'For loop initial assignment overwrites variable $i.',
+				39,
+			],
+			[
+				'For loop initial assignment overwrites variable $j.',
+				39,
+			],
+			[
+				'For loop initial assignment overwrites variable $i.',
+				50,
+			],
+			[
+				'For loop initial assignment overwrites variable $i.',
+				54,
+			],
+		]);
+	}
+
+}

tests/Rules/ForLoop/data/data.php

@@ -0,0 +1,62 @@
+<?php
+
+namespace OverwriteVariablesWithForLoopInit;
+
+class Foo{
+
+	public function simple(int $i): void
+	{
+		for($i = 0; $i < 10; ++$i){
+		
+		}
+
+		for($j = 0; $j < 10; ++$j){
+
+		}
+	}
+
+	public function multi(int $i, int $j): void
+	{
+		for($i = 0, $j = 0; $i < 10; ++$i){
+			
+		}
+
+		for($i = 0, $k = 0; $i < 10; ++$i){
+
+		}
+
+		for($k = 0, $l = 0; $k < 10; ++$k){
+
+		}
+	}
+
+	public function list(int $i, int $j, array $b): void
+	{
+		for(list($i, $j) = $b; $i < 10; ++$i){
+
+		}
+
+		for(list($i, list($j, $k)) = $b; $i < 10; ++$i){
+
+		}
+
+		for(list($k, list($l, $m)) = $b; $k < 10; ++$k){
+
+		}
+	}
+
+	public function array(int $i, array $b): void
+	{
+		for([$i, $j] = $b; $i < 10; ++$i){
+
+		}
+
+		for([$i, [$j, $k]] = $b; $i < 10; ++$i){
+
+		}
+
+		for([$k, [$l, $m]] = $b; $k < 10; ++$k){
+
+		}
+	}
+}