array_flip() for constant arrays

Author: ondrejmirtes

src/Type/Php/ArrayFlipFunctionReturnTypeExtension.php

@@ -8,9 +8,11 @@
 use PHPStan\Reflection\ParametersAcceptorSelector;
 use PHPStan\Type\Accessory\NonEmptyArrayType;
 use PHPStan\Type\ArrayType;
+use PHPStan\Type\Constant\ConstantArrayTypeBuilder;
 use PHPStan\Type\DynamicFunctionReturnTypeExtension;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
+use PHPStan\Type\TypeUtils;
 use function count;
 
 class ArrayFlipFunctionReturnTypeExtension implements DynamicFunctionReturnTypeExtension
@@ -30,6 +32,25 @@ public function getTypeFromFunctionCall(FunctionReflection $functionReflection,
 		$array = $functionCall->getArgs()[0]->value;
 		$argType = $scope->getType($array);
 
+		$constantArrays = TypeUtils::getOldConstantArrays($argType);
+		if (count($constantArrays) > 0) {
+			$flipped = [];
+			foreach ($constantArrays as $constantArray) {
+				$builder = ConstantArrayTypeBuilder::createEmpty();
+				foreach ($constantArray->getKeyTypes() as $i => $keyType) {
+					$valueType = $constantArray->getValueTypes()[$i];
+					$builder->setOffsetValueType(
+						ArrayType::castToArrayKeyType($valueType),
+						$keyType,
+						$constantArray->isOptionalKey($i),
+					);
+				}
+				$flipped[] = $builder->getArray();
+			}
+
+			return TypeCombinator::union(...$flipped);
+		}
+
 		if ($argType->isArray()->yes()) {
 			$keyType = $argType->getIterableKeyType();
 			$itemType = $argType->getIterableValueType();

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -995,6 +995,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-7563.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-7764.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-5845.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/array-flip-constant.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/array-flip-constant.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace ArrayFlipConstantArray;
+
+use function array_flip;
+use function PHPStan\Testing\assertType;
+
+class Foo
+{
+
+	public function doFoo(): void
+	{
+		$allowlist = ['name', 'description', 'author', 'type', 'homepage', 'require', 'require-dev', 'stability', 'license', 'autoload'];
+		assertType('array{name: 0, description: 1, author: 2, type: 3, homepage: 4, require: 5, require-dev: 6, stability: 7, license: 8, autoload: 9}', array_flip($allowlist));
+	}
+
+	public function doOptional(): void
+	{
+		$allowlist = ['name', 'description', 'author', 'type', 'homepage', 'require', 'require-dev', 'stability', 'license', 'autoload'];
+		if (rand(0, 1)) {
+			$allowlist[] = 'config';
+		}
+		assertType('array{name: 0, description: 1, author: 2, type: 3, homepage: 4, require: 5, require-dev: 6, stability: 7, license: 8, autoload: 9, config?: 10}', array_flip($allowlist));
+	}
+
+}