Support narrowing down via in_array with enum cases

src/Type/Php/InArrayFunctionTypeSpecifyingExtension.php

@@ -46,6 +46,7 @@ public function specifyTypes(FunctionReflection $functionReflection, FuncCall $n
 		if (
 			$context->truthy()
 			|| count(TypeUtils::getConstantScalars($arrayValueType)) > 0
+			|| count(TypeUtils::getEnumCaseObjects($arrayValueType)) > 0
 		) {
 			return $this->typeSpecifier->create(
 				$node->getArgs()[0]->value,

src/Type/TypeUtils.php

@@ -7,6 +7,7 @@
 use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantIntegerType;
 use PHPStan\Type\Constant\ConstantStringType;
+use PHPStan\Type\Enum\EnumCaseObjectType;
 use PHPStan\Type\Generic\TemplateType;
 use function array_merge;
 
@@ -173,6 +174,14 @@ public static function getConstantScalars(Type $type): array
 		return self::map(ConstantScalarType::class, $type, false);
 	}
 
+	/**
+	 * @return EnumCaseObjectType[]
+	 */
+	public static function getEnumCaseObjects(Type $type): array
+	{
+		return self::map(EnumCaseObjectType::class, $type, false);
+	}
+
 	/**
 	 * @internal
 	 * @return ConstantArrayType[]

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -640,6 +640,7 @@ public function dataFileAsserts(): iterable
 		if (PHP_VERSION_ID >= 80100) {
 			yield from $this->gatherAssertTypes(__DIR__ . '/data/enums.php');
 			yield from $this->gatherAssertTypes(__DIR__ . '/data/enums-import-alias.php');
+			yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-7176.php');
 		}
 
 		if (PHP_VERSION_ID >= 80000) {

tests/PHPStan/Analyser/data/bug-7176.php

@@ -0,0 +1,32 @@
+<?php declare(strict_types = 1); // lint >= 8.1
+
+namespace Bug7176;
+
+use function PHPStan\Testing\assertType;
+
+enum Suit
+{
+	case Hearts;
+	case Diamonds;
+	case Clubs;
+	case Spades;
+}
+
+function test(Suit $x): string {
+	if ($x === Suit::Clubs) {
+		assertType('Bug7176\Suit::Clubs', $x);
+		return 'WORKS';
+	}
+	assertType('Bug7176\Suit::Diamonds|Bug7176\Suit::Hearts|Bug7176\Suit::Spades', $x);
+
+	if (in_array($x, [Suit::Spades], true)) {
+		assertType('Bug7176\Suit::Spades', $x);
+		return 'DOES NOT WORK';
+	}
+	assertType('Bug7176\Suit::Diamonds|Bug7176\Suit::Hearts', $x);
+
+	return match ($x) {
+		Suit::Hearts => 'a',
+		Suit::Diamonds => 'b',
+	};
+}

tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php

@@ -194,4 +194,12 @@ public function testBug7095(): void
 		$this->analyse([__DIR__ . '/data/bug-7095.php'], []);
 	}
 
+	public function testBug7176(): void
+	{
+		if (PHP_VERSION_ID < 80100) {
+			$this->markTestSkipped('Test requires PHP 8.1.');
+		}
+		$this->analyse([__DIR__ . '/data/bug-7176.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-7176.php

@@ -0,0 +1,28 @@
+<?php declare(strict_types = 1); // lint >= 8.1
+
+namespace Bug7176;
+
+enum Suit
+{
+	case Hearts;
+	case Diamonds;
+	case Clubs;
+	case Spades;
+}
+
+function test(Suit $x): string {
+	if ($x === Suit::Clubs) {
+		return 'WORKS';
+	}
+	// Suit::Clubs is correctly eliminated from possible values
+
+	if (in_array($x, [Suit::Spades], true)) {
+		return 'DOES NOT WORK';
+	}
+	// Suit::Spades is not eliminated from possible values
+
+	return match ($x) { // no error is expected here
+		Suit::Hearts => 'a',
+		Suit::Diamonds => 'b',
+	};
+}