Fix #2301 - do a naive projection of template params

src/Psalm/Internal/Type/AssertionReconciler.php

@@ -2066,11 +2066,22 @@ class AssertionReconciler extends \Psalm\Type\Reconciler
                     $atomic_comparison_results
                 );
 
-                if ($atomic_contained_by || $atomic_comparison_results->type_coerced) {
+                if ($atomic_contained_by) {
                     $has_local_match = true;
-                    if ($atomic_comparison_results->type_coerced) {
+
-                        $matching_atomic_types[] = $existing_type_part;
+                    if ($atomic_comparison_results->type_coerced
+                        && get_class($new_type_part) === Type\Atomic\TNamedObject::class
+                        && $existing_type_part instanceof Type\Atomic\TGenericObject
+                    ) {
+                        // this is a hack - it's not actually rigorous, as the params may be different
+                        $matching_atomic_types[] = new Type\Atomic\TGenericObject(
+                            $new_type_part->value,
+                            $existing_type_part->type_params
+                        );
                     }
+                } elseif ($atomic_comparison_results->type_coerced) {
+                    $has_local_match = true;
+                    $matching_atomic_types[] = $existing_type_part;
                 }
 
                 if (($new_type_part instanceof Type\Atomic\TGenericObject

tests/Template/ClassTemplateExtendsTest.php

@@ -2424,6 +2424,41 @@ class ClassTemplateExtendsTest extends TestCase
                         return new Right(new B());
                     }'
             ],
+            'refineGenericWithInstanceof' => [
+                '<?php
+                    /** @template T */
+                    interface Maybe {}
+
+                    /**
+                     * @template T
+                     * @implements Maybe<T>
+                     */
+                    class Some implements Maybe {
+                        /** @var T */
+                        private $value;
+
+                        /** @psalm-param T $value */
+                        public function __construct($value) {
+                            $this->value = $value;
+                        }
+
+                        /** @psalm-return T */
+                        public function extract() { return $this->value; }
+                    }
+
+                    /**
+                     * @psalm-return Maybe<int>
+                     */
+                    function repository(): Maybe {
+                        return new Some(5);
+                    }
+
+                    $maybe = repository();
+
+                    if ($maybe instanceof Some) {
+                        $anInt = $maybe->extract();
+                    }'
+            ],
         ];
     }