Improve array filter return type on php8

src/Type/Php/ArrayFilterFunctionReturnTypeHelper.php

@@ -16,6 +16,7 @@
 use PHPStan\Analyser\MutatingScope;
 use PHPStan\Analyser\Scope;
 use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Php\PhpVersion;
 use PHPStan\Reflection\ReflectionProvider;
 use PHPStan\ShouldNotHappenException;
 use PHPStan\TrinaryLogic;
@@ -47,7 +48,10 @@ final class ArrayFilterFunctionReturnTypeHelper
 	private const USE_KEY = 2;
 	private const USE_ITEM = 3;
 
-	public function __construct(private ReflectionProvider $reflectionProvider)
+	public function __construct(
+		private ReflectionProvider $reflectionProvider,
+		private PhpVersion $phpVersion,
+	)
 	{
 	}
 
@@ -67,6 +71,10 @@ public function getType(Scope $scope, ?Expr $arrayArg, ?Expr $callbackArg, ?Expr
 		}
 
 		if ($arrayArgType instanceof MixedType) {
+			if ($this->phpVersion->throwsValueErrorForInternalFunctions()) {
+				return new ArrayType(new MixedType(), new MixedType());
+			}
+
 			return new BenevolentUnionType([
 				new ArrayType(new MixedType(), new MixedType()),
 				new NullType(),

tests/PHPStan/Analyser/LegacyNodeScopeResolverTest.php

@@ -4854,7 +4854,7 @@ public static function dataArrayFunctions(): array
 				'array_filter($withPossiblyFalsey)',
 			],
 			[
-				'(array|null)',
+				PHP_VERSION_ID < 80000 ? '(array|null)' : 'array',
 				'array_filter($mixed)',
 			],
 			[

tests/PHPStan/Analyser/nsrt/array-filter.php → tests/PHPStan/Analyser/nsrt/array-filter-php7.php

@@ -1,6 +1,6 @@
-<?php
+<?php // lint < 8.0
 
-namespace ArrayFilter;
+namespace ArrayFilterPHP7;
 
 use function PHPStan\Testing\assertType;
 

tests/PHPStan/Analyser/nsrt/array-filter-php8.php

@@ -0,0 +1,42 @@
+<?php // lint >= 8.0
+
+namespace ArrayFilterPHP8;
+
+use function PHPStan\Testing\assertType;
+
+function withoutAnyArgs(): void
+{
+	$filtered1 = array_filter();
+	assertType('array', $filtered1);
+}
+
+/**
+ * @param mixed $var1
+ */
+function withMixedInsteadOfArray($var1): void
+{
+	$filtered1 = array_filter($var1);
+	assertType('array', $filtered1);
+}
+
+/**
+ * @param array<string, bool|float|int|string> $map1
+ * @param array<string, bool|float|int|string> $map2
+ * @param array<string, bool|float|int|string> $map3
+ */
+function withoutCallback(array $map1, array $map2, array $map3): void
+{
+	$filtered1 = array_filter($map1);
+	assertType('array<string, float|int<min, -1>|int<1, max>|non-falsy-string|true>', $filtered1);
+
+	$filtered2 = array_filter($map2, null, ARRAY_FILTER_USE_KEY);
+	assertType('array<string, float|int<min, -1>|int<1, max>|non-falsy-string|true>', $filtered2);
+
+	$filtered3 = array_filter($map3, null, ARRAY_FILTER_USE_BOTH);
+	assertType('array<string, float|int<min, -1>|int<1, max>|non-falsy-string|true>', $filtered3);
+}
+
+function invalidCallableName(array $arr) {
+	assertType('*ERROR*', array_filter($arr, ''));
+	assertType('*ERROR*', array_filter($arr, '\\'));
+}