Preserve generics after usort() call

Author: ondrejmirtes

src/Analyser/NodeScopeResolver.php

@@ -146,6 +146,7 @@
 use PHPStan\Type\Generic\TemplateTypeVariance;
 use PHPStan\Type\Generic\TemplateTypeVarianceMap;
 use PHPStan\Type\IntegerType;
+use PHPStan\Type\IntersectionType;
 use PHPStan\Type\MixedType;
 use PHPStan\Type\NeverType;
 use PHPStan\Type\NullType;
@@ -3119,20 +3120,27 @@ static function (?Type $offsetType, Type $valueType, bool $optional) use (&$arra
 
 	private function getArraySortFunctionType(Type $type): Type
 	{
-		if (!$type->isArray()->yes()) {
-			return $type;
-		}
-
 		$isIterableAtLeastOnce = $type->isIterableAtLeastOnce();
 		if ($isIterableAtLeastOnce->no()) {
 			return $type;
 		}
 
-		$newArrayType = AccessoryArrayListType::intersectWith(new ArrayType(new IntegerType(), $type->getIterableValueType()));
-		if ($isIterableAtLeastOnce->yes()) {
-			$newArrayType = TypeCombinator::intersect($newArrayType, new NonEmptyArrayType());
-		}
-		return $newArrayType;
+		return TypeTraverser::map($type, static function (Type $type, callable $traverse) use ($isIterableAtLeastOnce): Type {
+			if ($type instanceof UnionType || $type instanceof IntersectionType) {
+				return $traverse($type);
+			}
+
+			if (!$type instanceof ArrayType) {
+				return $type;
+			}
+
+			$newArrayType = AccessoryArrayListType::intersectWith(new ArrayType(new IntegerType(), $type->getIterableValueType()));
+			if ($isIterableAtLeastOnce->yes()) {
+				$newArrayType = TypeCombinator::intersect($newArrayType, new NonEmptyArrayType());
+			}
+
+			return $newArrayType;
+		});
 	}
 
 	private function getFunctionThrowPoint(

tests/PHPStan/Analyser/data/sort.php

@@ -5,6 +5,7 @@
 use function PHPStan\Testing\assertNativeType;
 use function PHPStan\Testing\assertType;
 use function sort;
+use function usort;
 
 class Foo
 {
@@ -128,3 +129,25 @@ public function notArray(): void
 		assertType("'foo'", $arr);
 	}
 }
+
+class Bar
+{
+
+	/**
+	 * @template T
+	 * @param T&list<array{a: scalar, b: true}> $array
+	 * @return list<T>
+	 */
+	public function doFoo(array $array)
+	{
+		assertType('list<array{a: bool|float|int|string, b: true}>&T (method Sort\Bar::doFoo(), argument)', $array);
+		usort($array, function (array $a, array $b) {
+			return $a['a'] <=> $b['a'];
+		});
+
+		assertType('list<array{a: bool|float|int|string, b: true}>&T (method Sort\Bar::doFoo(), argument)', $array);
+
+		return $array;
+	}
+
+}