Merge pull request #6503 from orklah/TClassString_inference

src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php

@@ -1173,6 +1173,8 @@ class AssertionFinder
                         $literal_class_strings[] = $atomic_type->value;
                     } elseif ($atomic_type instanceof Type\Atomic\TTemplateParamClass) {
                         $literal_class_strings[] = $atomic_type->param_name;
+                    } elseif ($atomic_type instanceof Type\Atomic\TClassString && $atomic_type->as !== 'object') {
+                        $literal_class_strings[] = $atomic_type->as;
                     }
                 }
 

tests/ClassLikeStringTest.php

@@ -458,6 +458,23 @@ class ClassLikeStringTest extends TestCase
                         }
                     }',
             ],
+            'instanceofClassStringNotLiteral' => [
+                '<?php
+                    final class Z {
+                    /**
+                     * @psalm-var class-string<stdClass> $class
+                     */
+                    private string $class = stdClass::class;
+
+                    public function go(object $object): ?stdClass {
+                        $a = $this->class;
+                        if ($object instanceof $a) {
+                            return $object;
+                        }
+                        return null;
+                    }
+                }'
+            ],
             'returnTemplatedClassString' => [
                 '<?php
                     /**