Reindex constant arrays via shuffle

src/Analyser/NodeScopeResolver.php

@@ -1921,6 +1921,17 @@ static function (?Type $offsetType, Type $valueType, bool $optional) use (&$arra
 				$scope = $scope->assignVariable('http_response_header', new ArrayType(new IntegerType(), new StringType()));
 			}
 
+			if (isset($functionReflection) && $functionReflection->getName() === 'shuffle') {
+				$arrayArg = $expr->getArgs()[0]->value;
+				$arrayArgType = $scope->getType($arrayArg);
+
+				if ($arrayArgType instanceof ConstantArrayType) {
+					$arrayArgType = $arrayArgType->getValuesArray();
+				}
+
+				$scope = $scope->specifyExpressionType($arrayArg, $arrayArgType, $arrayArgType);
+			}
+
 			if (
 				isset($functionReflection)
 				&& $functionReflection->getName() === 'array_splice'

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -743,6 +743,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6070.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6108.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-1516.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6138.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6174.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/../Rules/Methods/data/bug-5749.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-5675.php');

tests/PHPStan/Analyser/data/bug-6138.php

@@ -0,0 +1,29 @@
+<?php declare(strict_types = 1);
+
+namespace Bug6138;
+
+use function PHPStan\Testing\assertType;
+
+$indexed = [
+	1,
+	2,
+	3,
+];
+$associative = [
+	'a' => 1,
+	'b' => 2,
+	'c' => 3,
+];
+$unordered = [
+	0 => 1,
+	3 => 2,
+	42 => 3,
+];
+
+shuffle( $indexed );
+shuffle( $associative );
+shuffle( $unordered );
+
+assertType( 'array{0, 1, 2}', array_keys( $indexed ) );
+assertType( 'array{0, 1, 2}', array_keys( $associative ) );
+assertType( 'array{0, 1, 2}', array_keys( $unordered ) );