Fix #2170 - allow @method annotations to override inherited immutable ones

src/Psalm/Internal/Analyzer/MethodAnalyzer.php

@@ -613,6 +613,7 @@ class MethodAnalyzer extends FunctionLikeAnalyzer
 
         if ($guide_method_storage->external_mutation_free
             && !$implementer_method_storage->external_mutation_free
+            && !$guide_method_storage->mutation_free_inferred
         ) {
             if (IssueBuffer::accepts(
                 new MissingImmutableAnnotation(

tests/ImmutableAnnotationTest.php

@@ -219,6 +219,23 @@ class ImmutableAnnotationTest extends TestCase
                         }
                     }'
             ],
+            'allowMethodOverriding' => [
+                '<?php
+                    class A {
+                        private string $a;
+
+                        public function __construct(string $a) {
+                            $this->a = $a;
+                        }
+
+                        public function getA() : string {
+                            return $this->a;
+                        }
+                    }
+
+                    /** @method string getA() */
+                    class B extends A {}',
+            ],
         ];
     }