Best practices for logical const

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On Sunday, 16 February 2014 at 04:46:34 UTC, Steven Schveighoffer 
wrote:
> It is safe if you can guarantee the input is ultimately 
> mutable. But there is no way to enforce such a guarantee. It is 
> on the caller to make sure that is true.
>
> I don't see why inout should be identified as any different 
> from const in this respect. You could just as easily say the 
> same thing about const.
>
> -Steve

Which is what I said in an earlier post. Wouldn't you be able to 
do this with a template somehow?

template LogicalConst(T)
if (isMutable!T)
{
     alias LogicalConst = inout(T);
}

void bumpWithConstArg(T)(ref LogicalConst!T t)
{
     //Compiler error if you try to modify t
     //t += 1;

     //Fine, cast it to mutable then modify
     //Nothing unsafe here because we verified t is mutable
     cast(T)t += 1;
}

void main()
{
     immutable n = 0;
     //No IFTI match because n is immutable
     bumpWithConstArg(n);

     auto m = 0;
     //Okay, m is mutable
     bumpWithConstArg(m);
}

This doesn't actually work, but this is just off the top of my 
head.