Why do I get this error when casting to an immutable or shared byRef return type?

[Mike Parker via Digitalmars-d-learn]

On Sunday, 19 June 2016 at 10:45:25 UTC, Gary Willoughby wrote:
> On Sunday, 19 June 2016 at 10:35:59 UTC, Gary Willoughby wrote:
>> ...
>
> A more correct example:

In the second example, the problem is this:

alias Type = Unqual!(T);

You are declaring the function to return T, which in your example 
is either int, const(int), immutable(int), or shared(int), but 
are returning a plain int in every case. This is fine for 
const(int), since non-const can implicitly convert to const. That 
is not the case for immutable(int) or shared(int). If you take 
out the alias to Unqual!T and replace both remaining instances of 
Type with T, then it works.