rust-lang / rust-lang/libs-team

ACP: Implement `TryFromIterator<T>` trait to compliment `FromIterator<T>` trait.

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api-change-proposal
Dominant language
Rust
Stars
178
Forks
28
Avg merge
15m
Merged PRs (30d)
1

Description

Proposal

Problem statement

I want to compliment the FromIterator<T> trait with a TryFromIterator<T> trait as that would basically be a fallible alternative to FromIterator<T>, it would be the same but the trait would have an Error field and the function would return a Result<R, Self::Error>.

Motivating examples or use cases

A use case I recently had was this one, basically the use cases for his would be making iterator implementations safer.

Solution sketch

My solution for this ACP is basically this one

pub trait TryFromIterator<T>: Sized {
    type Error;

    fn try_from_iter<I: IntoIterator<Item = T>>(iter: I) -> Result<Self, Self::Error>;
}

Or something similar

Alternatives

Probably making this a crate in crates.io doesn't make much sense, the alternatives to this is implementing it per project.

Links and related work

This thread literally solves the problem.

What happens now?

This issue contains an API change proposal (or ACP) and is part of the libs-api team feature lifecycle. Once this issue is filed, the libs-api team will review open proposals as capability becomes available. Current response times do not have a clear estimate, but may be up to several months.

Possible responses

The libs team may respond in various different ways. First, the team will consider the problem (this doesn't require any concrete solution or alternatives to have been proposed):

  • We think this problem seems worth solving, and the standard library might be the right place to solve it.
  • We think that this probably doesn't belong in the standard library.

Second, if there's a concrete solution:

  • We think this specific solution looks roughly right, approved, you or someone else should implement this. (Further review will still happen on the subsequent implementation PR.)
  • We're not sure this is the right solution, and the alternatives or other materials don't give us enough information to be sure about that. Here are some questions we have that aren't answered, or rough ideas about alternatives we'd want to see discussed.

Contributor guide

No contributing guide indexed for this repository

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the linked pre-RFC discussion and the Rust libs-team feature lifecycle before considering implementation. The issue provides only a trait sketch and no repository files or tests to change. Done currently means a libs-api decision on the problem and proposed API; implementation would require a later approved issue or pull request.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
api
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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