Bleeding edge - report catch with exception that is not thrown in the try block

Author: ondrejmirtes

conf/config.level4.neon

@@ -18,6 +18,8 @@ rules:
 	- PHPStan\Rules\TooWideTypehints\TooWideFunctionReturnTypehintRule
 
 conditionalTags:
+	PHPStan\Rules\Exceptions\CatchWithUnthrownExceptionRule:
+		phpstan.rules.rule: %featureToggles.preciseExceptionTracking%
 	PHPStan\Rules\DeadCode\UnusedPrivateConstantRule:
 		phpstan.rules.rule: %featureToggles.unusedClassElements%
 	PHPStan\Rules\DeadCode\UnusedPrivateMethodRule:
@@ -147,6 +149,9 @@ services:
 		tags:
 			- phpstan.rules.rule
 
+	-
+		class: PHPStan\Rules\Exceptions\CatchWithUnthrownExceptionRule
+
 	-
 		class: PHPStan\Rules\TooWideTypehints\TooWideMethodReturnTypehintRule
 		arguments:

phpstan-baseline.neon

@@ -110,6 +110,16 @@ parameters:
 			count: 1
 			path: src/PhpDoc/Tag/VarTag.php
 
+		-
+			message: "#^Dead catch \\- PHPStan\\\\BetterReflection\\\\Identifier\\\\Exception\\\\InvalidIdentifierName is never thrown in the try block\\.$#"
+			count: 2
+			path: src/Reflection/BetterReflection/BetterReflectionProvider.php
+
+		-
+			message: "#^Dead catch \\- PHPStan\\\\BetterReflection\\\\NodeCompiler\\\\Exception\\\\UnableToCompileNode\\|PHPStan\\\\BetterReflection\\\\Reflection\\\\Exception\\\\NotAClassReflection\\|PHPStan\\\\BetterReflection\\\\Reflection\\\\Exception\\\\NotAnInterfaceReflection is never thrown in the try block\\.$#"
+			count: 1
+			path: src/Reflection/BetterReflection/BetterReflectionProvider.php
+
 		-
 			message: "#^Only booleans are allowed in a negated boolean, int\\|false given\\.$#"
 			count: 1

src/Analyser/NodeScopeResolver.php

@@ -55,6 +55,7 @@
 use PHPStan\File\FileReader;
 use PHPStan\Node\BooleanAndNode;
 use PHPStan\Node\BooleanOrNode;
+use PHPStan\Node\CatchWithUnthrownExceptionNode;
 use PHPStan\Node\ClassConstantsNode;
 use PHPStan\Node\ClassMethodsNode;
 use PHPStan\Node\ClassPropertiesNode;
@@ -1183,6 +1184,7 @@ private function processStmtNode(
 					$throwPoints = $newThrowPoints;
 
 					if (count($matchingThrowPoints) === 0) {
+						$nodeCallback(new CatchWithUnthrownExceptionNode($catchNode, $catchType), $scope);
 						continue;
 					}
 

src/Node/CatchWithUnthrownExceptionNode.php

@@ -0,0 +1,46 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Node;
+
+use PhpParser\Node\Stmt\Catch_;
+use PhpParser\NodeAbstract;
+use PHPStan\Type\Type;
+
+class CatchWithUnthrownExceptionNode extends NodeAbstract implements VirtualNode
+{
+
+	private Catch_ $originalNode;
+
+	private Type $caughtType;
+
+	public function __construct(Catch_ $originalNode, Type $caughtType)
+	{
+		parent::__construct($originalNode->getAttributes());
+		$this->originalNode = $originalNode;
+		$this->caughtType = $caughtType;
+	}
+
+	public function getOriginalNode(): Catch_
+	{
+		return $this->originalNode;
+	}
+
+	public function getCaughtType(): Type
+	{
+		return $this->caughtType;
+	}
+
+	public function getType(): string
+	{
+		return 'PHPStan_Node_CatchWithUnthrownExceptionNode';
+	}
+
+	/**
+	 * @return string[]
+	 */
+	public function getSubNodeNames(): array
+	{
+		return [];
+	}
+
+}

src/Rules/Exceptions/CatchWithUnthrownExceptionRule.php

@@ -0,0 +1,32 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Exceptions;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Node\CatchWithUnthrownExceptionNode;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\Type\VerbosityLevel;
+
+/**
+ * @implements Rule<CatchWithUnthrownExceptionNode>
+ */
+class CatchWithUnthrownExceptionRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return CatchWithUnthrownExceptionNode::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		return [
+			RuleErrorBuilder::message(
+				sprintf('Dead catch - %s is never thrown in the try block.', $node->getCaughtType()->describe(VerbosityLevel::typeOnly()))
+			)->line($node->getLine())->build(),
+		];
+	}
+
+}

tests/PHPStan/Rules/Exceptions/CatchWithUnthrownExceptionRuleTest.php

@@ -0,0 +1,38 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Exceptions;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+class CatchWithUnthrownExceptionRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new CatchWithUnthrownExceptionRule();
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/unthrown-exception.php'], [
+			[
+				'Dead catch - Throwable is never thrown in the try block.',
+				12,
+			],
+			[
+				'Dead catch - Exception is never thrown in the try block.',
+				21,
+			],
+			[
+				'Dead catch - Throwable is never thrown in the try block.',
+				38,
+			],
+			[
+				'Dead catch - RuntimeException is never thrown in the try block.',
+				47,
+			],
+		]);
+	}
+
+}

tests/PHPStan/Rules/Exceptions/data/unthrown-exception.php

@@ -0,0 +1,63 @@
+<?php
+
+namespace UnthrownException;
+
+class Foo
+{
+
+	public function doFoo(): void
+	{
+		try {
+			$foo = 1;
+		} catch (\Throwable $e) {
+			// pass
+		}
+	}
+
+	public function doBar(): void
+	{
+		try {
+			$foo = 1;
+		} catch (\Exception $e) {
+			// pass
+		}
+	}
+
+	/** @throws \InvalidArgumentException */
+	public function throwIae(): void
+	{
+
+	}
+
+	public function doBaz(): void
+	{
+		try {
+			$this->throwIae();
+		} catch (\InvalidArgumentException $e) {
+
+		} catch (\Throwable $e) {
+			// dead
+		}
+	}
+
+	public function doLorem(): void
+	{
+		try {
+			$this->throwIae();
+		} catch (\RuntimeException $e) {
+ 			// dead
+		} catch (\Throwable $e) {
+
+		}
+	}
+
+	public function doIpsum(): void
+	{
+		try {
+			$this->throwIae();
+		} catch (\Throwable $e) {
+
+		}
+	}
+
+}