How to get an inout constructor working with a template wrapper

[aliak]

On Friday, 27 July 2018 at 14:38:27 UTC, Steven Schveighoffer 
wrote:
> On 7/27/18 9:29 AM, aliak wrote:
>> Ok, thanks to Simen from another post [0], I just figured out 
>> what the correct constructor and factory method for a template 
>> wrapper should be:
>> 
>> https://run.dlang.io/is/S4vHzL
>> 
>> struct W(T) {
>>      T val;
>>      this(U : T, this This)(auto ref U val) {
>>          this.val = val;
>>      }
>> }
>> 
>> auto wrap(T)(auto ref T t) {
>>      return W!T(t);
>> }
>> 
>> Seems to catch all cases!
>
> And instantiate a new template for all mutabilities. Whereas 
> inout would only instantiate one (and disallows modification of 
> val if not const or immutable).
>
> -Steve

If you change the ctor to be inout then you get (from the link 
above):

onlineapp.d(4): Error: cannot implicitly convert expression val 
of type onlineapp.C to inout(C)
onlineapp.d(28): Error: template instance 
`onlineapp.W!(C).W.__ctor!(C)` error instantiating
onlineapp.d(4): Error: cannot implicitly convert expression val 
of type S1 to inout(S1)
onlineapp.d(44): Error: template instance 
`onlineapp.W!(S1).W.__ctor!(S1)` error instantiating
onlineapp.d(4): Error: cannot implicitly convert expression val 
of type onlineapp.C to inout(C)
onlineapp.d(9): Error: template instance 
`onlineapp.W!(C).W.__ctor!(C)` error instantiating
onlineapp.d(52):        instantiated from here: wrap!(C)
onlineapp.d(4): Error: cannot implicitly convert expression val 
of type const(C) to inout(const(C))
onlineapp.d(9): Error: template instance 
`onlineapp.W!(const(C)).W.__ctor!(const(C))` error instantiating
onlineapp.d(53):        instantiated from here: wrap!(const(C))

Am I applying inout incorrectly?