How to declare function with the same call signature as another?

[Tofu Ninja via Digitalmars-d-learn]

On Sunday, 20 November 2016 at 11:23:37 UTC, Nicholas Wilson 
wrote:
> On Sunday, 20 November 2016 at 11:19:24 UTC, Tofu Ninja wrote:
>> I feel like this should be simple but I can't seem to figure 
>> it out. How do I declare a function to have the same call 
>> signature as another function/callable type?
>>
>> Like if I have:
>>
>> alias Sig = int function(int x, int y);
>>
>> How do I define a function such that it will have the same 
>> call signature as Sig? How do I take into account all the 
>> extra stuff that can go into a function signature like the 
>> argument attributes and the return type attributes etc.?
>>
>> Another way to phrase this question would be, how do I pass a 
>> function signature into a template and actually define 
>> functions with it?
>>
>> Related question, if I have Sig, how would I define DeltaSig 
>> to be exactly the same as Sig but with an extra parameter at 
>> the start or end of the parameter list?
>>
>> Thanks :)
> import std.traits;
> ReturnType!Sig func(Parameters!Sig args)
> {
>     //...
> }

This does not seem to account for return type attributes or 
function attributes. Eg:

alias Sig = ref int function() @nogc;
ReturnType!Sig func(Parameters!Sig args) {
	// func is missing ref on return type and is not @nogc
	static int g;
	return g;
}

How should I account for these things?