Rule for checking matching type between switch condition and case condition

Author: ondrejmirtes

rules.neon

@@ -36,3 +36,8 @@ services:
 		class: PHPStan\Rules\StrictCalls\StrictFunctionCallsRule
 		tags:
 			- phpstan.rules.rule
+
+	-
+		class: PHPStan\Rules\SwitchConditions\MatchingTypeInSwitchCaseConditionRule
+		tags:
+			- phpstan.rules.rule

src/Rules/SwitchConditions/MatchingTypeInSwitchCaseConditionRule.php

@@ -0,0 +1,49 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\SwitchConditions;
+
+class MatchingTypeInSwitchCaseConditionRule implements \PHPStan\Rules\Rule
+{
+
+	/** @var \PhpParser\PrettyPrinter\Standard */
+	private $printer;
+
+	public function __construct(\PhpParser\PrettyPrinter\Standard $printer)
+	{
+		$this->printer = $printer;
+	}
+
+	public function getNodeType(): string
+	{
+		return \PhpParser\Node\Stmt\Switch_::class;
+	}
+
+	/**
+	 * @param \PhpParser\Node\Stmt\Switch_ $node
+	 * @param \PHPStan\Analyser\Scope $scope
+	 * @return string[] errors
+	 */
+	public function processNode(\PhpParser\Node $node, \PHPStan\Analyser\Scope $scope): array
+	{
+		$messages = [];
+		$conditionType = $scope->getType($node->cond);
+		foreach ($node->cases as $case) {
+			if ($case->cond === null) {
+				continue;
+			}
+
+			$caseType = $scope->getType($case->cond);
+			if ($conditionType->isSupersetOf($caseType)->no()) {
+				$messages[] = sprintf(
+					'Switch condition type (%s) does not match case condition %s (%s).',
+					$conditionType->describe(),
+					$this->printer->prettyPrintExpr($case->cond),
+					$caseType->describe()
+				);
+			}
+		}
+
+		return $messages;
+	}
+
+}

tests/Rules/SwitchConditions/MatchingTypeInSwitchCaseConditionRuleTest.php

@@ -0,0 +1,37 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\SwitchConditions;
+
+use PHPStan\Rules\Rule;
+
+class MatchingTypeInSwitchCaseConditionRuleTest extends \PHPStan\Testing\RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new MatchingTypeInSwitchCaseConditionRule(new \PhpParser\PrettyPrinter\Standard());
+	}
+
+	public function testRule()
+	{
+		$this->analyse([__DIR__ . '/data/matching-type.php'], [
+			[
+				'Switch condition type (int) does not match case condition \'test\' (string).',
+				8,
+			],
+			[
+				'Switch condition type (int) does not match case condition 1 > 2 (bool).',
+				8,
+			],
+			[
+				'Switch condition type (string) does not match case condition 1 (int).',
+				19,
+			],
+			[
+				'Switch condition type (string) does not match case condition 1 > 2 (bool).',
+				19,
+			],
+		]);
+	}
+
+}

tests/Rules/SwitchConditions/data/matching-type.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace SwitchConditions;
+
+$int = 1;
+$string = '1';
+
+switch ($int) {
+	case 1:
+		break;
+	case 'test':
+		break;
+	case 1 > 2:
+		break;
+	default:
+		return;
+}
+
+switch ($string) {
+	case 1:
+		break;
+	case 'test':
+		break;
+	case 1 > 2:
+		break;
+	default:
+		return;
+}