From 2c0dda3212bdd63df57d146822aa07ff0d412840 Mon Sep 17 00:00:00 2001
From: Ondrej Mirtes <ondrej@mirtes.cz>
Date: Mon, 29 Mar 2021 17:43:49 +0200
Subject: [PATCH] Match expression - report usage of void

---
 conf/config.level2.neon                       |  1 +
 .../UsageOfVoidMatchExpressionRule.php        | 35 +++++++++++++++++++
 .../UsageOfVoidMatchExpressionRuleTest.php    | 33 +++++++++++++++++
 .../Rules/Comparison/data/void-match.php      | 28 +++++++++++++++
 4 files changed, 97 insertions(+)
 create mode 100644 src/Rules/Comparison/UsageOfVoidMatchExpressionRule.php
 create mode 100644 tests/PHPStan/Rules/Comparison/UsageOfVoidMatchExpressionRuleTest.php
 create mode 100644 tests/PHPStan/Rules/Comparison/data/void-match.php

diff --git a/conf/config.level2.neon b/conf/config.level2.neon
index bb27e9271e..c284232e28 100644
--- a/conf/config.level2.neon
+++ b/conf/config.level2.neon
@@ -11,6 +11,7 @@ rules:
 	- PHPStan\Rules\Cast\InvalidCastRule
 	- PHPStan\Rules\Cast\InvalidPartOfEncapsedStringRule
 	- PHPStan\Rules\Cast\PrintRule
+	- PHPStan\Rules\Comparison\UsageOfVoidMatchExpressionRule
 	- PHPStan\Rules\Functions\IncompatibleDefaultParameterTypeRule
 	- PHPStan\Rules\Generics\ClassAncestorsRule
 	- PHPStan\Rules\Generics\ClassTemplateTypeRule
diff --git a/src/Rules/Comparison/UsageOfVoidMatchExpressionRule.php b/src/Rules/Comparison/UsageOfVoidMatchExpressionRule.php
new file mode 100644
index 0000000000..8494d0c2b2
--- /dev/null
+++ b/src/Rules/Comparison/UsageOfVoidMatchExpressionRule.php
@@ -0,0 +1,35 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Comparison;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\Type\VoidType;
+
+/**
+ * @implements Rule<Node\Expr\Match_>
+ */
+class UsageOfVoidMatchExpressionRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return Node\Expr\Match_::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		$matchResultType = $scope->getType($node);
+		if (
+			$matchResultType instanceof VoidType
+			&& !$scope->isInFirstLevelStatement()
+		) {
+			return [RuleErrorBuilder::message('Result of match expression (void) is used.')->build()];
+		}
+
+		return [];
+	}
+
+}
diff --git a/tests/PHPStan/Rules/Comparison/UsageOfVoidMatchExpressionRuleTest.php b/tests/PHPStan/Rules/Comparison/UsageOfVoidMatchExpressionRuleTest.php
new file mode 100644
index 0000000000..bf873a965c
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/UsageOfVoidMatchExpressionRuleTest.php
@@ -0,0 +1,33 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Comparison;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<UsageOfVoidMatchExpressionRule>
+ */
+class UsageOfVoidMatchExpressionRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new UsageOfVoidMatchExpressionRule();
+	}
+
+	public function testRule(): void
+	{
+		if (PHP_VERSION_ID < 80000 && !self::$useStaticReflectionProvider) {
+			$this->markTestSkipped('Test requires PHP 8.0.');
+		}
+
+		$this->analyse([__DIR__ . '/data/void-match.php'], [
+			[
+				'Result of match expression (void) is used.',
+				21,
+			],
+		]);
+	}
+
+}
diff --git a/tests/PHPStan/Rules/Comparison/data/void-match.php b/tests/PHPStan/Rules/Comparison/data/void-match.php
new file mode 100644
index 0000000000..f2cfbb22ff
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/void-match.php
@@ -0,0 +1,28 @@
+<?php // lint >= 8.0
+
+namespace VoidMatch;
+
+class Foo
+{
+
+	public function doFoo(): void
+	{
+
+	}
+
+	public function doBar(int $i): void
+	{
+		match ($i) {
+			1 => $this->doFoo(),
+			2 => $this->doFoo(),
+			default => $this->doFoo(),
+		};
+
+		$a = match ($i) {
+			1 => $this->doFoo(),
+			2 => $this->doFoo(),
+			default => $this->doFoo(),
+		};
+	}
+
+}