> and you can instantly generalize to anything that isn't necessarily a `Result` but has the same general structure.
>
> closes the opportunity
The door isn't closed for this, `?` works with a "carrier" trait, which lets you extend the operator. Now, it's currently unstable, so right now you can't use it, but the door is wide open for the design of `Carrier` to be finalized.
This was explicitly discussed and thought out before ? was stabilized. It's just that ? was stabilized before Carrier.
The compiler knows nothing about `Result`. There are very few structs that it knows anything about, and these all have to do with atomics or `UnsafeCell` or other intrinsic-based primitives that you don't need to reimplement out-of-tree anyway. It knows a few traits, like Add and Copy and Carrier, which can be used to extend operators and stuff.
> The door isn't closed for this, `?` works with a "carrier" trait, which lets you extend the operator. Now, it's currently unstable, so right now you can't use it, but the door is wide open for the design of `Carrier` to be finalized.
Oh, OK that at least sound like sound "defensive design" -- good to hear :). However, what happens if `Carrier` needs to be radically redesigned, e.g. to account for HKTs or Rank-N types (or something similarly 'crazy').
Carrier itself is unstable, so it can be redesigned into whatever it wants to be. The only restriction is that it should continue to work with Results the way it does now, and that's an easy thing to maintain. It could be made into an HKT trait thingymajig. It will probably just be a trait with two associated types, this is very close to HKT anyway.
>
> closes the opportunity
The door isn't closed for this, `?` works with a "carrier" trait, which lets you extend the operator. Now, it's currently unstable, so right now you can't use it, but the door is wide open for the design of `Carrier` to be finalized.
This was explicitly discussed and thought out before ? was stabilized. It's just that ? was stabilized before Carrier.
The compiler knows nothing about `Result`. There are very few structs that it knows anything about, and these all have to do with atomics or `UnsafeCell` or other intrinsic-based primitives that you don't need to reimplement out-of-tree anyway. It knows a few traits, like Add and Copy and Carrier, which can be used to extend operators and stuff.