Use better metric for a properly mismatching type

src/Psalm/Internal/Analyzer/MethodAnalyzer.php

@@ -908,9 +908,17 @@ class MethodAnalyzer extends FunctionLikeAnalyzer
                             }
                         }
                     } else {
+                        if (TypeAnalyzer::isContainedBy(
+                            $codebase,
+                            $implementer_method_storage_param_type,
+                            $guide_method_storage_param_type,
+                            !$guide_classlike_storage->user_defined,
+                            !$guide_classlike_storage->user_defined
+                        )) {
                             if (IssueBuffer::accepts(
-                            new ImplementedParamTypeMismatch(
+                                new MoreSpecificImplementedParamType(
-                                'Argument ' . ($i + 1) . ' of ' . $cased_implementer_method_id . ' has wrong type \'' .
+                                    'Argument ' . ($i + 1) . ' of ' . $cased_implementer_method_id
+                                        . ' has the more specific type \'' .
                                         $implementer_method_storage_param_type->getId() . '\', expecting \'' .
                                         $guide_method_storage_param_type->getId() . '\' as defined by ' .
                                         $cased_guide_method_id,
@@ -921,6 +929,22 @@ class MethodAnalyzer extends FunctionLikeAnalyzer
                             )) {
                                 return false;
                             }
+                        } else {
+                            if (IssueBuffer::accepts(
+                                new ImplementedParamTypeMismatch(
+                                    'Argument ' . ($i + 1) . ' of ' . $cased_implementer_method_id
+                                        . ' has wrong type \'' .
+                                        $implementer_method_storage_param_type->getId() . '\', expecting \'' .
+                                        $guide_method_storage_param_type->getId() . '\' as defined by ' .
+                                        $cased_guide_method_id,
+                                    $implementer_method_storage->params[$i]->location
+                                        ?: $code_location
+                                ),
+                                $suppressed_issues
+                            )) {
+                                return false;
+                            }
+                        }
                     }
                 }
             }

tests/MethodSignatureTest.php

@@ -943,6 +943,19 @@ class MethodSignatureTest extends TestCase
                 'error_message' => 'MethodSignatureMismatch',
                 ['MoreSpecificImplementedParamType']
             ],
+            'preventOneOfUnionMoreSpecific' => [
+                '<?php
+                    class A {
+                        /** @param string|int $s */
+                        public function foo($s) : void {}
+                    }
+
+                    class B extends A {
+                        /** @param string $s */
+                        public function foo($s) : void {}
+                    }',
+                'error_message' => 'MoreSpecificImplementedParamType',
+            ],
             'preventImplementingSerializableWithType' => [
                 '<?php
                     class Foo implements \Serializable {