Transients or scoped immutability

[Jesse Phillips]

bearophile Wrote:

> This post contains uncooked ideas.
> 
> I'd like to create data structures:
> - That once created are immutable, so there is no risk to write on them, etc;
> - On the stack too, avoiding slower heap allocations and avoiding copying them from the mutable to the immutable version;
> - Avoiding to keep in the function name space a dead name of the mutable version of the data structure;
> - Avoiding calls to functions that may contain loops that DMD doesn't inline;
> - Avoiding too much complex code for the programmer.

There was talk in the past of allowing a pure function create and modify a class and return that class as immutable. This was a suggestion on how to create immutable classes. The details were never really hashed out, but maybe it is possible for any returned value (of a pure function) to be implicitly converted to immutable.

To me it sounds really nice an clean, do you think it would work for you?