improve handling of scalar literals with in_array

src/Type/Php/InArrayFunctionTypeSpecifyingExtension.php

@@ -9,9 +9,13 @@
 use PHPStan\Analyser\TypeSpecifierAwareExtension;
 use PHPStan\Analyser\TypeSpecifierContext;
 use PHPStan\Reflection\FunctionReflection;
+use PHPStan\Type\BooleanType;
 use PHPStan\Type\Constant\ConstantBooleanType;
+use PHPStan\Type\Constant\ConstantStringType;
+use PHPStan\Type\ConstantScalarType;
 use PHPStan\Type\FunctionTypeSpecifyingExtension;
 use PHPStan\Type\TypeUtils;
+use PHPStan\Type\UnionType;
 
 class InArrayFunctionTypeSpecifyingExtension implements FunctionTypeSpecifyingExtension, TypeSpecifierAwareExtension
 {
@@ -39,7 +43,24 @@ public function specifyTypes(FunctionReflection $functionReflection, FuncCall $n
 			return new SpecifiedTypes([], []);
 		}
 
-		$arrayValueType = $scope->getType($node->getArgs()[1]->value)->getIterableValueType();
+		$needleType = $scope->getType($node->getArgs()[0]->value);
+		$arrayType = $scope->getType($node->getArgs()[1]->value);
+		$arrayValueType = $arrayType->getIterableValueType();
+
+
+		if ($arrayValueType instanceof UnionType|| $arrayValueType instanceof ConstantScalarType) {
+			if ($arrayType->isIterableAtLeastOnce()->yes()) {
+				if ($arrayValueType instanceof ConstantScalarType && $needleType instanceof ConstantScalarType) {
+					if ($arrayValueType->getValue() !== $needleType->getValue()) {
+						return new SpecifiedTypes();
+					}
+				} else {
+					return new SpecifiedTypes();
+				}
+			} elseif ($needleType instanceof ConstantScalarType) {
+				return new SpecifiedTypes();
+			}
+		}
 
 		if (
 			$context->truthy()

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -510,6 +510,7 @@ public function dataFileAsserts(): iterable
 
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/eval-implicit-throw.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-5628.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-5668.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/bug-5668.php

@@ -0,0 +1,42 @@
+<?php declare(strict_types=1);
+
+namespace Bug5668;
+
+use function PHPStan\Testing\assertType;
+
+class Foo
+{
+
+	/**
+	 * @param array<int, 'test'|'bar'> $in
+	 */
+	function has(array $in): void
+	{
+		assertType('bool', in_array('test', $in, true));
+	}
+
+	/**
+	 * @param array<int, 'test'> $in
+	 */
+	function has2(array $in): void
+	{
+		assertType('bool', in_array('test', $in, true));
+	}
+
+	/**
+	 * @param non-empty-array<int, 'test'|'bar'> $in
+	 */
+	function has3(array $in): void
+	{
+		assertType('bool', in_array('test', $in, true));
+	}
+
+
+	/**
+	 * @param non-empty-array<int, 'test'> $in
+	 */
+	function has4(array $in): void
+	{
+		assertType('true', in_array('test', $in, true));
+	}
+}