D safety! New Feature?

[H.Loom via Digitalmars-d]

On Thursday, 4 August 2016 at 18:22:52 UTC, Mark "J" Twain wrote:
> Marking a widget immutable is not the same as having an 
> ImmutableWidget. Can you see the difference?

Yes, you're thinking here of logical vs physical immutability.

> I assure you there is. The immutable keyword only prevents data 
> manipulation, it does not change the interface. For simple 
> primitives, there is not much difference, but for larger 
> complex types, the immutable keyword doesn't cut it.
>
> immutable Queue!int q1;
> ImmutableQueue!int q2;

I don't get you well because D has actually the ability to use 
immutable as part of the type. This feature is called the type 
constructors.

immutable Queue : attribute or storage class
immutable(Queue): part of type