Fix return type of array_reverse() with $preserve_keys = true for lists

Author: herndlm

src/Type/Php/ArrayReverseFunctionReturnTypeExtension.php

@@ -5,6 +5,8 @@
 use PhpParser\Node\Expr\FuncCall;
 use PHPStan\Analyser\Scope;
 use PHPStan\Reflection\FunctionReflection;
+use PHPStan\Type\Accessory\NonEmptyArrayType;
+use PHPStan\Type\ArrayType;
 use PHPStan\Type\DynamicFunctionReturnTypeExtension;
 use PHPStan\Type\NeverType;
 use PHPStan\Type\Type;
@@ -43,6 +45,16 @@ public function getTypeFromFunctionCall(FunctionReflection $functionReflection,
 			return TypeCombinator::union(...$results);
 		}
 
+		if ($preserveKeys) {
+			// Remove list
+			$newArrayType = new ArrayType($type->getIterableKeyType(), $type->getIterableValueType());
+			if ($type->isIterableAtLeastOnce()->yes()) {
+				$newArrayType = TypeCombinator::intersect($newArrayType, new NonEmptyArrayType());
+			}
+
+			return $newArrayType;
+		}
+
 		return $type;
 	}
 

tests/PHPStan/Analyser/nsrt/array-reverse.php

@@ -46,4 +46,17 @@ public function constantArrays(array $a, array $b): void
 		assertType('array{\'bar\', \'foo\'}|array{bar: 19, foo: 17}', array_reverse($b));
 		assertType('array{19: \'bar\', 17: \'foo\'}|array{bar: 19, foo: 17}', array_reverse($b, true));
 	}
+
+	/**
+	 * @param list<string> $a
+	 * @param non-empty-list<string> $b
+	 */
+	public function list(array $a, array $b): void
+	{
+		assertType('list<string>', array_reverse($a));
+		assertType('array<int<0, max>, string>', array_reverse($a, true));
+
+		assertType('non-empty-list<string>', array_reverse($b));
+		assertType('non-empty-array<int<0, max>, string>', array_reverse($b, true));
+	}
 }