Vadim Lopatin:
Const sub-tree is object itself and its data. Reference to object is outside of tree. Why references to const object should be const?
There was a very long discussion on this. I think the short answer is to keep the syntax and semantics composed of a sufficiently low number of parts (in D you don't have syntax to tell apart objects from their references).
A D user wrote a patch to implement what you ask for, but it was essentially left to die in GitHub.
But there's Rebindable in Phobos. Bye, bearophile
