Noissue - use static_assert for SFINAE for better error messaging

compiled/StringMap.h

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 28 matching lines @@
 struct StringHash
 {
   size_t operator()(const String& key) const
   {
     return StringMap_internal::stringHash(key);
   }
 };
 
 namespace StringMap_internal
 {
-  template<typename Key,
-    class = typename std::enable_if<std::is_base_of<String, Key>::value>::type>
+  template<typename Key>
   struct StringSetEntry
   {
+    static_assert(std::is_base_of<String, Key>::value, "Type of Key should be based on String");
     typedef Key key_type;
     typedef const String& key_type_cref;
     typedef size_t size_type;
 
     key_type first;
 
     StringSetEntry(key_type_cref key = key_type())
     {
       if (!key.is_invalid())
         first.reset(key);
@@ skipping 47 matching lines @@
   };
 }
 
 using StringSet = Set<StringMap_internal::StringSetEntry<DependentString>>;
 
 template<typename Value>
 using StringMap = Map<StringMap_internal::StringMapEntry<DependentString, Value>>;
 template<typename Value>
 using OwnedStringMap = Map<StringMap_internal::StringMapEntry<OwnedString, Value>>;
 ABP_NS_END