Meta tracking issue for impl Trait

This issue tracks the progress of impl Trait in general.

This issue is not for discussion about specific extensions to impl Trait and only exists to provide links to other places that track the progress of specific issues. If you wish to discuss some subject related to impl Trait, please find an existing appropriate issue below or create an new issue and comment here with a link to the newly created issue.

The impl Trait related issues currently on deck are as follows:

Open RFCs:

None.

#65481 Allow impl Trait in trait method return values.

@sighoya

@sighoya @Aaron1011 @mark-i-m @CryZe This issue is not for general discussion about impl Trait. It's only intended to collect links.

This issue is not for discussion about specific extensions to impl Trait and only exists to provide links to other places that track the progress of specific issues. If you wish to discuss some subject related to impl Trait, please find an existing appropriate issue below or create an new issue and comment here with a link to the newly created issue.

Trait definitions is your second example, covered by #29661. Your first example is trait implementations, which is covered by RFC 2515 (#63063), specifically the last example of RFC 2515 § Guide-level explanation § Type alias, and it currently works on nightly with #![feature(type_alias_impl_trait)].

@Nemo157

Thanks @Nemo157. I would find amendment to the issue text here to make clear that the link to #63063 also encompasses trait implementations and that the sub-link to #29661 is only about associated type defaults helpful. At the moment, the implication of the text is that #63063 is only about "bare" type aliases and #29661 is about impl Trait in associated types.

Hello, does this include allowing impl Trait in structs? (something RFC2071 may have solved)

E.g. -

struct Session {
    client: websocket::sync::Client<impl websocket::sync::Stream>
}

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
   --> src/main.rs:139:37
    |
139 |     client: websocket::sync::Client<impl websocket::sync::Stream>,
    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The current workaround for doing this is quite unergonomic -

use anyhow::Result;
use websocket;

fn main() -> Result<()> {
    let session = create_session()?;
    Ok(())
}

struct Session<T: websocket::sync::Stream> {
    client: websocket::sync::Client<T>,
}

fn create_session() -> Result<Session<impl websocket::sync::Stream>> {
    let client = websocket::ClientBuilder::new("ws://...")?.connect_insecure()?;
    Ok(Session { client })
}

Source

vs if this was implemented -

use anyhow::Result;
use websocket;

fn main() -> Result<()> {
    let session = Session::new()?;
    Ok(())
}

struct Session {
    client: websocket::sync::Client<impl websocket::sync::Stream>
}

impl Session {
	fn new() -> Result<Self> {
	    let client = websocket::ClientBuilder::new("ws://...")?.connect_insecure()?;
	    Ok(Session { client })
	}
}

Is there a tracking issue for named existential types? The original tracking issue (#44685) was closed as a duplicate of #34511, which was closed in favor of this issue, but I don't see named existential types mentioned anywhere here...

@ibraheemdev

Is there a tracking issue for named existential types?

@ibraheemdev #63063
https://rust-lang.github.io/rfcs/2515-type_alias_impl_trait.html

move memory discovery to the Architecture trait

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Meta tracking issue for `impl Trait` #63066

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Meta tracking issue for impl Trait #63066

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kevincox commented on Oct 16, 2019

sighoya commented on Nov 17, 2019

Aaron1011 commented on Nov 17, 2019

CryZe commented on Nov 17, 2019

sighoya commented on Nov 17, 2019

mark-i-m commented on Nov 17, 2019

CryZe commented on Nov 17, 2019

Centril commented on Nov 17, 2019

1 remaining item

Nemo157 commented on Jun 25, 2020

rphmeier commented on Jun 25, 2020

devxpy commented on Sep 6, 2020

ibraheemdev commented on Jan 3, 2021

memoryruins commented on Jan 3, 2021

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Meta tracking issue for `impl Trait` #63066