immutable postblit unusable?

[Cauterite]

On Sunday, 11 February 2018 at 08:25:41 UTC, Jonathan M Davis 
wrote:
> …

Thanks, I couldn't have asked for a more thorough explanation.
Especially that __xpostblit detail, which I now vaguely recall 
seeing in the runtime code.

Sounds like making `this(this) immutable` illegal is the way to 
go.

I don't have anything to add about the `const` problem though.