use string representation of symbols for back reference comparison

Author: rainers

src/dmangle.d

@@ -178,7 +178,7 @@ public:
     {
         // cannot put C++ classes into a hash table, tries to call toHash
         size_t[void*] types;
-        size_t[void*] symbols;
+        size_t[string] symbols;
         size_t[void*] idents;
     }
     OutBuffer* buf;
@@ -209,12 +209,13 @@ public:
     {
         version(useBackref)
         {
-            if (auto p = cast(void*)s in symbols)
+            string id = s.getIdent();
+            if (auto p = id in symbols)
             {
                 buf.printf("%d$", cast(int)*p);
                 return true;
             }
-            symbols[cast(void*)s] = symbols.length;
+            symbols[id] = symbols.length;
         }
         return false;
     }