How to extract the AA type?

[Steven Schveighoffer]

On 12/13/17 11:30 AM, jmh530 wrote:
> On Wednesday, 13 December 2017 at 16:00:32 UTC, Steven Schveighoffer wrote:
>> A nice puzzle for those template gurus out there.
>>
>> I have a function like this:
>>
>> auto foo(T: V[K], V, K)(T t)
>> {
>>    RealAAType!(T, V, K) aa = t;
>>    return aa;
>> }
>>
>> So I need to know what to write RealAAType. What I'm looking for is a 
>> mechanism to write the exact AA type that is passed in. RealAAType 
>> should be an AA, and nothing else.
>>
> [snip]
> 
> How about:
> 
> template RealAAType!(T, V, K)
> {
>      import std.traits : CopyConstness;
> 
>      alias RealAAType = CopyConstness!(T, V[K]);
> }

Yes, that seems to work, I was worried that something like this would 
give me multiple type modifiers (.e.g const(const(int)[int])

Now, I need to figure out how to do this in object.d :)

BTW, the PR that spurred this for reference: 
https://github.com/dlang/druntime/pull/1992

-Steve