Fix match of union of enums

src/Analyser/NodeScopeResolver.php

@@ -3446,14 +3446,20 @@ static function (Node $node, Scope $scope) use ($nodeCallback): void {
 									$expr->cond,
 									$enumCase,
 								);
-							} elseif (count($unusedIndexedEnumCases[$loweredFetchedClassName]) === 1) {
-								$hasAlwaysTrueCond = true;
-
-								// force "always true"
-								$armConditionScope = $armConditionScope->addTypeToExpression(
-									$expr->cond,
-									$enumCase,
-								);
+							} else {
+								$unusedCasesCount = 0;
+								foreach ($unusedIndexedEnumCases as $cases) {
+									$unusedCasesCount += count($cases);
+								}
+								if ($unusedCasesCount === 1) {
+									$hasAlwaysTrueCond = true;
+
+									// force "always true"
+									$armConditionScope = $armConditionScope->addTypeToExpression(
+										$expr->cond,
+										$enumCase,
+									);
+								}
 							}
 
 							$this->processExprNode($stmt, $cond, $armConditionScope, $nodeCallback, $deepContext);

tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php

@@ -581,4 +581,13 @@ public function testBug9879(): void
 		$this->analyse([__DIR__ . '/data/bug-9879.php'], []);
 	}
 
+	public function testBug11313(): void
+	{
+		if (PHP_VERSION_ID < 80100) {
+			$this->markTestSkipped('Test requires PHP 8.1.');
+		}
+
+		$this->analyse([__DIR__ . '/data/bug-11313.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-11313.php

@@ -0,0 +1,23 @@
+<?php // lint >= 8.1
+
+namespace Bug11313;
+
+enum Foo: string
+{
+	case CaseOne = 'one';
+	case CaseTwo = 'two';
+}
+
+enum Bar: string
+{
+	case CaseThree = 'Three';
+}
+
+function test(Foo|Bar $union): bool
+{
+	return match ($union) {
+		Bar::CaseThree,
+		Foo::CaseOne => true,
+		Foo::CaseTwo => false,
+	};
+}