Use wider class-string when combining class strings with intersections

Fixes #10799

Author: weirdan

src/Psalm/Internal/Type/TypeCombiner.php

@@ -1005,7 +1005,20 @@ private static function scrapeStringProperties(
             if (!$type->as_type) {
                 $combination->class_string_types['object'] = new TObject();
             } else {
-                $combination->class_string_types[$type->as] = $type->as_type;
+                if (isset($combination->class_string_types[$type->as])
+                    && $combination->class_string_types[$type->as] instanceof TNamedObject
+                ) {
+                    if ($combination->class_string_types[$type->as]->extra_types === []) {
+                        // do nothing, existing type is wider or the same
+                    } elseif ($type->as_type->extra_types === []) {
+                        $combination->class_string_types[$type->as] = $type->as_type;
+                    } else {
+                        // todo: figure out what to do with class-string<A&B>|class-string<A&C>
+                        $combination->class_string_types[$type->as] = $type->as_type;
+                    }
+                } else {
+                    $combination->class_string_types[$type->as] = $type->as_type;
+                }
             }
         } elseif ($type instanceof TLiteralString) {
             if ($combination->strings !== null && count($combination->strings) < $literal_limit) {

tests/TypeCombinationTest.php

@@ -940,6 +940,13 @@ public function providerTestValidTypeCombination(): array
                     '"0"',
                 ],
             ],
+            'unionOfClassStringAndClassStringWithIntersection' => [
+                'class-string<IFoo>',
+                [
+                    'class-string<IFoo>',
+                    'class-string<IFoo & IBar>',
+                ],
+            ],
         ];
     }
 

tests/TypeParseTest.php

@@ -1148,6 +1148,14 @@ public function testIntMaskOfWithValidValueOf(): void
         $this->assertSame('int-mask-of<value-of<A::FOO>>', $docblock_type->getId());
     }
 
+    public function testUnionOfClassStringAndClassStringWithIntersection(): void
+    {
+        $this->assertSame(
+            'class-string<IFoo>',
+            (string) Type::parseString('class-string<IFoo>|class-string<IFoo&IBar>'),
+        );
+    }
+
     public function testReflectionTypeParse(): void
     {
         if (!function_exists('Psalm\Tests\someFunction')) {