"Why there is no good library Head Const in D?" answered

[Q. Schroll]

There were some minor errors. Three times, I wrote "Final" 
meaning "head_const".

> For every non-static member variable V v in a struct T, Final!T 
> must have a property v returning a Final!V.

That should read: For every ... variable V v in a struct T, 
head_const!T must have a property v returning a head_const!V.

> First, the author of the struct must be aware it might be used 
> as a type parameter for Final.

That should read: ... it might be used as a type parameter for 
head_const.

Sorry if you were confused reading over these passages.