Code behaves incorrectly if it is compiled in std.functional

[ketmar via Digitalmars-d]

here's dustmited source:

template unaryFun(alias fun, string parmName="a") {
   static if (is(typeof(fun)))
     auto unaryFun(ElementType) (auto ElementType __a) {
       mixin("alias " ~ parmName ~ " = __a ;");
       return mixin(fun);
     } else static if (needOpCallAlias) {
       unaryFun fun;
     }
}


unittest {
   cast(void)unaryFun!"a+1"(41); // silence warning
}


unittest {
   struct Foo2 {
     int fun (int n) pure nothrow @safe @nogc { return n; }
   }

   import std.traits;
   pragma(msg, ParameterTypeTuple!(typeof(Foo2.fun)));
}


# dmd -c -o- -unittest test.d to see `(auto int)`

note that after removing any attribute from `Foo2.foo` will emit 
correct `(int)`.