Fix false positive UnhandledMatchError throw point

Author: rajyan

src/Analyser/NodeScopeResolver.php

@@ -2561,6 +2561,7 @@ static function (Node $node, Scope $scope) use ($nodeCallback): void {
 			$matchScope = $scope;
 			$armNodes = [];
 			$hasDefaultCond = false;
+			$hasAlwaysTrueCond = false;
 			foreach ($expr->arms as $arm) {
 				if ($arm->conds === null) {
 					$hasDefaultCond = true;
@@ -2586,6 +2587,10 @@ static function (Node $node, Scope $scope) use ($nodeCallback): void {
 					$hasYield = $hasYield || $armCondResult->hasYield();
 					$throwPoints = array_merge($throwPoints, $armCondResult->getThrowPoints());
 					$armCondExpr = new BinaryOp\Identical($expr->cond, $armCond);
+					$armCondType = $armCondResult->getScope()->getType($armCondExpr);
+					if ($armCondType instanceof ConstantBooleanType && $armCondType->getValue()) {
+						$hasAlwaysTrueCond = true;
+					}
 					$armCondScope = $armCondResult->getScope()->filterByFalseyValue($armCondExpr);
 					if ($filteringExpr === null) {
 						$filteringExpr = $armCondExpr;
@@ -2611,7 +2616,7 @@ static function (Node $node, Scope $scope) use ($nodeCallback): void {
 			}
 
 			$remainingType = $matchScope->getType($expr->cond);
-			if (!$hasDefaultCond && !$remainingType instanceof NeverType) {
+			if (!$hasDefaultCond && !$hasAlwaysTrueCond && !$remainingType instanceof NeverType) {
 				$throwPoints[] = ThrowPoint::createExplicit($scope, new ObjectType(UnhandledMatchError::class), $expr, false);
 			}
 

tests/PHPStan/Rules/Exceptions/ThrowsVoidMethodWithExplicitThrowPointRuleTest.php

@@ -5,6 +5,8 @@
 use PHPStan\Rules\Rule;
 use PHPStan\Testing\RuleTestCase;
 use ThrowsVoidMethod\MyException;
+use UnhandledMatchError;
+use const PHP_VERSION_ID;
 
 /**
  * @extends RuleTestCase<ThrowsVoidMethodWithExplicitThrowPointRule>
@@ -96,4 +98,14 @@ public function testRule(bool $missingCheckedExceptionInThrows, array $checkedEx
 		$this->analyse([__DIR__ . '/data/throws-void-method.php'], $errors);
 	}
 
+	public function testBug6910(): void
+	{
+		if (PHP_VERSION_ID < 80000) {
+			$this->markTestSkipped('Test requires PHP 8.0.');
+		}
+		$this->missingCheckedExceptionInThrows = false;
+		$this->checkedExceptionClasses = [UnhandledMatchError::class];
+		$this->analyse([__DIR__ . '/data/bug-6910.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Exceptions/data/bug-6910.php

@@ -0,0 +1,43 @@
+<?php declare(strict_types = 1); // lint >= 8.0
+
+namespace Bug6910;
+
+class RedFish {}
+
+class BlueFish {}
+
+class Net {
+	public RedFish|BlueFish $heldFish;
+	public int $prop;
+
+	/**
+	 * @throws void
+	 */
+	public function dropFish(): void {
+		match ($this->heldFish instanceof RedFish) {
+			true => 'hello',
+			false => 'world',
+		};
+	}
+
+	/**
+	 * @throws void
+	 * @param 'hello'|'world' $string
+	 */
+	public function issetFish(string $string): void {
+		match ($string === 'hello') {
+			true => 'hello',
+			false => 'world',
+		};
+	}
+
+	/**
+	 * @throws void
+	 */
+	public function anotherFish(bool $bool): void {
+		match ($bool) {
+			true => 'hello',
+			false => 'world',
+		};
+	}
+}