No issue - Fallthrough attributes must be terminated with semicolon.

This also fixes building with Clang 15 on Linux.

js/src/irregexp/RegExpParser.cpp

@@ -987,7 +987,7 @@ RegExpParser<CharT>::ParseClassEscape(char16_t* char_class, widechar *value,
               }
               return true;
             }
-            MOZ_FALLTHROUGH
+            MOZ_FALLTHROUGH;
           default:
             if (!ParseClassCharacterEscape(value))
                 return false;

js/src/vm/RegExpObject.cpp

@@ -1558,7 +1558,7 @@ ParseRegExpFlags(const CharT* chars, size_t length, RegExpFlag* flagsOut, char16
                     return false;
                 break;
             }
-            MOZ_FALLTHROUGH
+            MOZ_FALLTHROUGH;
           default:
             return false;
         }