Could you show us some use cases for your proposal? What drove you to make this proposal?

cc @neild

IMO Something like Result is way too generic and would need it's own proposal.
You could also use 2 value iteration.

IMO Something like Result is way too generic and would need it's own proposal.
You could also use 2 value iteration.

Using product types to express sum types is an unreasonable thing in itself. I think we can't make any mistakes anymore. It's time to make some changes. Maybe this can be the first place to change.

I know there are currently some proposals related to the sum type, but nothing has changed for a long time and no one seems willing to move forward with them. The use of struct design here was forced to make some choices.

The convention in slices and maps is to call this “All” not “Iter”.

The proposed new iteration APIs in #61897 provide alternatives to existing functions which return a slice of results, permitting the caller to iterate over results without allocating the entire result slice.

net.Listener.Accept does not have have this flaw: It returns a single result at a time. It is not inconvenient to use. The proposed API here doesn't seem any simpler to use:

for {
  conn, err := listener.Accept()
  if err != nil {
    // handle error
  }
  // ...
}

vs.

for result := listener.Iter() {
  if result.IsErr() {
    // handle error
  }
  conn := result.Value()
  // ...
}

This is at most one line less code, or the same number of lines if we assign conn := result.Value().

Leaving aside the fact that Result really would need its own proposal, I don't think the added complexity of a second API for accepting connections can be justified here.

I wonder how many applications have more than a single call to Listener.Accept; extra syntactic convenience wouldn't help very often. And Accept is such a significant enough operation that perhaps it warrants being explicit within the loop, not hidden in an iterator.

Closing it, for no compelling reason other than to copy the same capabilities from rust.

And due to the lack of type system support for sum type, there has not been much change in usage.