Porting std.typecons to Phobos 3

[Paul Backus]

On Sunday, 17 November 2024 at 03:13:20 UTC, Jonathan M Davis 
wrote:
> e.g. in the case of Nullable [...] adding the ability to cast 
> to bool in addition to using hasValue (or whatever we call the 
> replacement for isNull)

https://github.com/dlang/phobos/pull/9039

> and adding the ability to dereference it (that way, it can be 
> used in if conditions just like a pointer, and templated code 
> could work with either pointers or Option/Maybe/Whatever ).

I don't think this is a great idea. Option!T has value semantics 
(w.r.t. the T value), but T* has reference semantics, so generic 
code that tries to work with both will likely fall into the same 
pitfalls that code using input ranges currently does.

> Personally, it's on my todo list to sit down and look through 
> how Rebindable and friends need to be reworked, since that's 
> kind of a mess, and some of it is potentially going to affect 
> how we deal with ranges.

Mathis Beer/FeepingCreature did a bunch of work on this, 
including a DConf talk [1]. Might be worth getting in touch with 
him.

[1] https://www.youtube.com/watch?v=eGX_fxlig8I