Private alias escaping -- is this a bug?

[Vlad Levenfeld via Digitalmars-d-learn]

On Saturday, 25 April 2015 at 23:51:05 UTC, rcorre wrote:
> I ran into this infuriatingly confusing situation just now:
>
> static assert(is(typeof(Parent.init.new Child) == 
> Parent.Child)); // fine
>
> alias P = Parent;
> alias T = Parent.Child;
>
> static assert(is(typeof(P.init.new T) == T)); // nope!
>
> Wat???
>
> After much confusion, I finally discovered this in my class:
>
> class Parent {
>     class Child { }
>     mixin MyMixin;
> }
>
> mixin Template MyMixin() {
>     private alias T = ...; // the culprit!
> }
>
> Should the private alias be able to escape? Is this a bug or 
> expected behavior?
>
> Also, is there a nice way to create template-level aliases in 
> mixin templates that don't leak into the class? MyMixin 
> generates multiple functions that all use T.

You could namespace them in a sense by defining a nested struct 
that contains the aliases.