Just watched this presentation : http://www.infoq.com/presentations/functional-pros-cons

Skip to minute 28 to understand what we are discussing here about the magical unique.

On Friday, 20 December 2013 at 22:40:16 UTC, Timon Gehr wrote:
>> http://wiki.dlang.org/DIP49
>> Improved points from version 1:
>> - Swap meanings of 'this(this) inout' and 'this(this) const'
>> - Inout postblit now covers all cheap (== not rebind indirections)
>> copies between same qualifiers
>>
>> Kenji Hara
>
> What about just mentioning the qualifiers of source and target of the copy explicitly?
>
> this(this){ ... } // mutable source, mutable target
> this(immutable this){ ... } // immutable source mutable target
> this(const this)immutable{ ... } // const source, immutable target
> this(const this)const{ ... } // const source, const target
> // ...
> this(inout this)inout{ ... } // source and target have the same qualifier
> // ...
> this(this)inout{ ... } // mutable source, arbitrary target
> // ...
> this(const this)inout{ ... } // const source, arbitrary target
>
> Whenever source and target are (potentially) incompatible, the postblit ensures that all fields with incompatible types in source and target are reinitialized.
>
> Only unique expressions convert to 'inout' anyway, hence the last signature above would correspond to unique postblit in the current proposal.
>
> This would be more explicit, strictly more expressive and require less special casing in the compiler implementation.

I agree, it will be the most powerful solution. And we should use the same rules for constructor behavior.

Also, we have strange rules in DIP 53:

> If mutable constructor is defined, if immutable constructor is not defined, it will be used for const object construction.

> If immutable constructor is defined, if mutable constructor is not defined, it will be used for const object construction.

What happens if we have both mutable and immutable constructors?

On 12/21/2013 03:57 AM, deadalnix wrote:
> Just watched this presentation :
> http://www.infoq.com/presentations/functional-pros-cons
>
> Skip to minute 28 to understand what we are discussing here about the
> magical unique.

At minute 28 he starts discussing Monads using Dart-like syntax.