Fix array_slice() with mixed argument

It was previously returning *NEVER*.

Author: jlherren

src/Type/Php/ArraySliceFunctionReturnTypeExtension.php

@@ -61,7 +61,14 @@ public function getTypeFromFunctionCall(
 
 $constantArrays = TypeUtils::getConstantArrays($valueType);
 if (count($constantArrays) === 0) {
-return TypeCombinator::union(...TypeUtils::getArrays($valueType));
+$arrays = TypeUtils::getArrays($valueType);
+if (count($arrays) !== 0) {
+return TypeCombinator::union(...$arrays);
+}
+return new ArrayType(
+new MixedType(),
+new MixedType()
+);
 }
 
 if (isset($functionCall->args[3])) {

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -10229,9 +10229,9 @@ public function dataBug3985(): array
 return $this->gatherAssertTypes(__DIR__ . '/data/bug-3985.php');
 }
 
-public function dataArraySliceNonEmpty(): array
+public function dataArraySlice(): array
 {
-return $this->gatherAssertTypes(__DIR__ . '/data/array-slice-non-empty.php');
+return $this->gatherAssertTypes(__DIR__ . '/data/array-slice.php');
 }
 
 public function dataBug3990(): array
@@ -10347,7 +10347,7 @@ public function dataBug4016(): array
  * @dataProvider dataBug2816
  * @dataProvider dataBug2816Two
  * @dataProvider dataBug3985
- * @dataProvider dataArraySliceNonEmpty
+ * @dataProvider dataArraySlice
  * @dataProvider dataBug3990
  * @dataProvider dataBug3991
  * @dataProvider dataBug3993

tests/PHPStan/Analyser/data/array-slice-non-empty.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace ArraySlice;
+
+use function PHPStan\Analyser\assertType;
+
+class Foo
+{
+
+/**
+ * @param non-empty-array $a
+ */
+public function nonEmpty(array $a): void
+{
+assertType('array', array_slice($a, 1));
+}
+
+/**
+ * @param mixed $arr
+ */
+public function fromMixed($arr): void
+{
+assertType('array', array_slice($arr, 1, 2));
+}
+
+/**
+ * @param array<int, bool> $arr1
+ * @param array<string, int> $arr2
+ */
+public function preserveTypes(array $arr1, array $arr2): void
+{
+assertType('array<int, bool>', array_slice($arr1, 1, 2));
+assertType('array<int, bool>', array_slice($arr1, 1, 2, true));
+assertType('array<string, int>', array_slice($arr2, 1, 2));
+assertType('array<string, int>', array_slice($arr2, 1, 2, true));
+}
+
+}