Base class' constructor is not implicitly inherited for immutable classes. A bug or a feature?

[Eugene Wissner via Digitalmars-d-learn]

On Wednesday, 19 July 2017 at 16:00:56 UTC, Piotr Mitana wrote:
> Hello, I have this code:
>
> immutable class Base
> {
> 	this() {}
> }
>
> immutable class Derived : Base {}
>
> void main()
> {
> 	new immutable Derived();
> }
>
> I'd like class Derived to automatically inherit the default 
> constructor from Base. However, this is not the case:
>
> main.d(6): Error: class main.Derived cannot implicitly generate 
> a default ctor when base class main.Base is missing a default 
> ctor
>
> Is it a bug or it should be like this?

Interesting that the same code without immutable works.