[TypeDeclaration] Map accessory string intersection to string in union return type (#8125)

ReturnUnionTypeRector inferred 0|(numeric-string&non-falsy-string) returns but IntersectionTypeMapper only handled object intersections, returning null for the string-accessory member and aborting the whole union. Map a pure-string intersection to string so int|string is added.

Author: TomasVotruba

rules-tests/TypeDeclaration/Rector/ClassMethod/ReturnUnionTypeRector/Fixture/int_or_numeric_string.php.inc

@@ -0,0 +1,57 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\ReturnUnionTypeRector\Fixture;
+
+final class IntOrNumericString
+{
+    private function getAssetSize(): int
+    {
+        return 1000;
+    }
+
+    public function getTotalFilesize($assets)
+    {
+        if (empty($assets)) {
+            return 0;
+        }
+
+        $size = $this->getAssetSize($assets);
+
+        if ($size) {
+            $size = (string) $size;
+        }
+
+        return $size;
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\ReturnUnionTypeRector\Fixture;
+
+final class IntOrNumericString
+{
+    private function getAssetSize(): int
+    {
+        return 1000;
+    }
+
+    public function getTotalFilesize($assets): int|string
+    {
+        if (empty($assets)) {
+            return 0;
+        }
+
+        $size = $this->getAssetSize($assets);
+
+        if ($size) {
+            $size = (string) $size;
+        }
+
+        return $size;
+    }
+}
+
+?>

src/PHPStanStaticTypeMapper/TypeMapper/IntersectionTypeMapper.php

@@ -5,6 +5,7 @@
 namespace Rector\PHPStanStaticTypeMapper\TypeMapper;
 
 use PhpParser\Node;
+use PhpParser\Node\Identifier;
 use PhpParser\Node\Name\FullyQualified;
 use PHPStan\PhpDocParser\Ast\Node as AstNode;
 use PHPStan\PhpDocParser\Ast\Type\ArrayShapeItemNode;
@@ -91,6 +92,11 @@ function (AstNode $astNode): int|IdentifierTypeNode {
      */
     public function mapToPhpParserNode(Type $type, string $typeKind): ?Node
     {
+        // accessory string types, e.g. "numeric-string&non-falsy-string", are just "string"
+        if ($type->isString()->yes()) {
+            return new Identifier('string');
+        }
+
         if (! $this->phpVersionProvider->isAtLeastPhpVersion(PhpVersionFeature::INTERSECTION_TYPES)) {
             return null;
         }