Min TAIT + GAT lifetime issue #86218

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1. ivan770

   added

   C-bugCategory: This is a bug.Category: This is a bug.

   on Jun 11, 2021
2. ivan770 commented on Jun 13, 2021

   

   ivan770

   on Jun 13, 2021

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   @rustbot label +T-compiler +F-type_alias_impl_trait +F-generic_associated_types +A-lifetimes +requires-nightly
3. rustbot

   added

   A-lifetimesArea: Lifetimes / regionsArea: Lifetimes / regions

   F-generic_associated_types`#![feature(generic_associated_types)]` a.k.a. GATs`#![feature(generic_associated_types)]` a.k.a. GATs

   F-type_alias_impl_trait`#[feature(type_alias_impl_trait)]``#[feature(type_alias_impl_trait)]`

   requires-nightlyThis issue requires a nightly compiler in some way. When possible, use a F-* label instead.This issue requires a nightly compiler in some way. When possible, use a F-* label instead.

   T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

   on Jun 13, 2021
4. b-naber commented on Jun 16, 2021

   

   b-naber

   on Jun 16, 2021

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   @rustbot claim
5. rustbot

   assigned

   b-naber

   on Jun 16, 2021
6. jackh726

   added

   F-min_type_alias_impl_trait

   and removed

   F-type_alias_impl_trait`#[feature(type_alias_impl_trait)]``#[feature(type_alias_impl_trait)]`

   on Jun 29, 2021
7. jackh726 commented on Oct 23, 2021

   

   jackh726

   on Oct 23, 2021

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   Updated and minimized example:

   #![feature(generic_associated_types)]
   #![feature(type_alias_impl_trait)]
   
   pub trait Stream {
       type Item;
   }
   
   impl Stream for () {
       type Item = i32;
   }
   
   trait Yay<AdditionalValue> {
       type InnerStream<'s>: Stream<Item = i32> + 's;
       fn foo<'s>() -> Self::InnerStream<'s>;
   }
   
   impl<'a> Yay<&'a ()> for () {
       type InnerStream<'s> = impl Stream<Item = i32> + 's;
       fn foo<'s>() -> Self::InnerStream<'s> { todo!() }
   }
8. jackh726 commented on Oct 23, 2021

   

   jackh726

   on Oct 23, 2021

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   Yeah, so somehow 'a is ending up in the substs for the opaque type impl Stream<Item = i32> + 's, and that isn't able to be proven.
9. jackh726 commented on Oct 23, 2021

   

   jackh726

   on Oct 23, 2021

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   GATs issue triage: not blocking. This requires the type_alias_impl_trait feature and seems to revolve around the substs for them, rather than a GATs issue.
10. jackh726

    added

    GATs-triaged

    on Oct 23, 2021
11. jackh726

    added

    F-type_alias_impl_trait`#[feature(type_alias_impl_trait)]``#[feature(type_alias_impl_trait)]`

    and removed

    F-min_type_alias_impl_trait

    on Mar 9, 2022
12. oli-obk commented on Mar 31, 2022

    

    oli-obk

    on Mar 31, 2022

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    @b-naber this issue has been fixed as a side effect of #95474

    ❤️React with ❤️1Reacted by Ivan Leshchenko
13. oli-obk

    moved this to Todo in type alias impl trait stabilizationon Sep 9, 2022
14. oli-obk

    added this to type alias impl trait stabilizationon Sep 9, 2022
15. oli-obk

    moved this from Todo to In Progress in type alias impl trait stabilizationon Sep 9, 2022
16. bors

    added a commit that references this issue on Sep 25, 2022

    Auto merge of rust-lang#95474 - oli-obk:tait_ub, r=jackh726

    ...

    This issue will close once commit f5193a9 is merged into the 'master' branch.

    f5193a9
17. bors

    closed this as completedin f5193a9on Sep 25, 2022
18. Repository owner moved this from In Progress to Done in type alias impl trait stabilizationon Sep 25, 2022
19. fmease

    added

    A-GATsArea: Generic associated types (GATs)Area: Generic associated types (GATs)

    on Nov 2, 2024