New VoidCastRule

Author: DanielEScherzer

src/Rules/Cast/VoidCastRule.php

@@ -0,0 +1,41 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Cast;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\DependencyInjection\RegisteredRule;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+
+/**
+ * @implements Rule<Node\Expr\Cast\Void_>
+ */
+#[RegisteredRule(level: 0)]
+final class VoidCastRule implements Rule
+{
+
+	public function __construct()
+	{
+	}
+
+	public function getNodeType(): string
+	{
+		return Node\Expr\Cast\Void_::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if ($scope->isInFirstLevelStatement()) {
+			return [];
+		}
+
+		return [
+			RuleErrorBuilder::message('The (void) cast cannot be used within an expression.')
+				->identifier('cast.void')
+				->nonIgnorable()
+				->build(),
+		];
+	}
+
+}

tests/PHPStan/Rules/Cast/VoidCastRuleTest.php

@@ -0,0 +1,37 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Cast;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<VoidCastRule>
+ */
+class VoidCastRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new VoidCastRule();
+	}
+
+	public function testPrintRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/void-cast.php'], [
+			[
+				'The (void) cast cannot be used within an expression.',
+				5,
+			],
+			[
+				'The (void) cast cannot be used within an expression.',
+				6,
+			],
+			[
+				'The (void) cast cannot be used within an expression.',
+				7,
+			],
+		]);
+	}
+
+}

tests/PHPStan/Rules/Cast/data/void-cast.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace VoidCast;
+
+$a = (void)$z;
+$b = (void)(1 + 1);
+var_dump( (void)$c );