Add NoncapturingCatchRule

conf/config.level0.neon

@@ -58,6 +58,7 @@ rules:
 	- PHPStan\Rules\Constants\FinalConstantRule
 	- PHPStan\Rules\Constants\NativeTypedClassConstantRule
 	- PHPStan\Rules\EnumCases\EnumCaseAttributesRule
+	- PHPStan\Rules\Exceptions\NoncapturingCatchRule
 	- PHPStan\Rules\Exceptions\ThrowExpressionRule
 	- PHPStan\Rules\Functions\ArrowFunctionAttributesRule
 	- PHPStan\Rules\Functions\ArrowFunctionReturnNullsafeByRefRule

src/Php/PhpVersion.php

@@ -41,6 +41,11 @@ public function supportsReturnCovariance(): bool
 		return $this->versionId >= 70400;
 	}
 
+	public function supportsNoncapturingCatches(): bool
+	{
+		return $this->versionId >= 80000;
+	}
+
 	public function supportsNativeUnionTypes(): bool
 	{
 		return $this->versionId >= 80000;

src/Rules/Exceptions/NoncapturingCatchRule.php

@@ -0,0 +1,46 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Exceptions;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Php\PhpVersion;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+
+/**
+ * @implements Rule<Node\Stmt\Catch_>
+ */
+class NoncapturingCatchRule implements Rule
+{
+
+	public function __construct(private PhpVersion $phpVersion)
+	{
+	}
+
+	public function getNodeType(): string
+	{
+		return Node\Stmt\Catch_::class;
+	}
+
+	/**
+	 * @param Node\Stmt\Catch_ $node
+	 */
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if ($this->phpVersion->supportsNoncapturingCatches()) {
+			return [];
+		}
+
+		if ($node->var !== null) {
+			return [];
+		}
+
+		return [
+			RuleErrorBuilder::message('Non-capturing catch is supported only on PHP 8.0 and later.')
+				->nonIgnorable()
+				->build(),
+		];
+	}
+
+}

tests/PHPStan/Rules/Exceptions/NoncapturingCatchRuleTest.php

@@ -0,0 +1,60 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Exceptions;
+
+use PHPStan\Php\PhpVersion;
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<NoncapturingCatchRule>
+ */
+class NoncapturingCatchRuleTest extends RuleTestCase
+{
+
+	private PhpVersion $phpVersion;
+
+	protected function getRule(): Rule
+	{
+		return new NoncapturingCatchRule($this->phpVersion);
+	}
+
+	public function dataRule(): array
+	{
+		return [
+			[
+				70400,
+				[
+					[
+						'Non-capturing catch is supported only on PHP 8.0 and later.',
+						12,
+					],
+					[
+						'Non-capturing catch is supported only on PHP 8.0 and later.',
+						21,
+					],
+				],
+			],
+			[
+				80000,
+				[],
+			],
+		];
+	}
+
+	/**
+	 * @dataProvider dataRule
+	 *
+	 * @param list<array{0: string, 1: int, 2?: string}> $expectedErrors
+	 */
+	public function testRule(int $phpVersion, array $expectedErrors): void
+	{
+		$this->phpVersion = new PhpVersion($phpVersion);
+
+		$this->analyse([
+			__DIR__ . '/data/noncapturing-catch.php',
+			__DIR__ . '/data/bug-8663.php',
+		], $expectedErrors);
+	}
+
+}

tests/PHPStan/Rules/Exceptions/data/bug-8663.php

@@ -0,0 +1,25 @@
+<?php // lint >= 8.0
+
+namespace Bug8663;
+
+/**
+ * Provides example to demonstrate an issue with PHPStan.
+ */
+class StanExample2
+{
+
+    /**
+     * An exception is caught but not captured.
+     *
+     * That's OK for PHP 8 but not for 7.4 - PHPStan does not report the issue.
+     */
+    public function catchExceptionsWithoutCapturing(): void
+    {
+        try {
+            print 'Lets do something nasty here.';
+            throw new \Exception('This is nasty');
+        } catch (\Exception) {
+            print 'Exception occured';
+        }
+    }
+}

tests/PHPStan/Rules/Exceptions/data/noncapturing-catch.php

@@ -0,0 +1,17 @@
+<?php // lint >= 8.0
+
+namespace NoncapturingCatch;
+
+class HelloWorld
+{
+
+	public function hello(): void
+	{
+		try {
+            throw new \Exception('Hello');
+        } catch (\Exception) {
+            echo 'Hi!';
+        }
+	}
+
+}