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Meta tracking issue for `impl Trait` #63066

Centril opened this issue Jul 28, 2019 · 0 comments


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commented Jul 28, 2019

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:

  • Label A-impl-trait

  • Permit type Foo = impl Bar;. #63063

    • Permit type Foo = impl Bar; in trait definitions. #29661
  • In const and static items and let bindings. #63065

  • Member constraints in region inference: #61997

  • Existential lifetimes. #60670

  • Support lifetime elision in argument position. #49287

  • Should we allow impl Trait after -> in fn types or parentheses sugar? #45994

  • Do we have to impose a DAG across all functions to allow for auto-safe leakage, or can we use some kind of deferral.

  • Should we permit specifying types if some parameters are implicit and some are explicit? e.g., fn foo<T>(x: impl Iterator<Item = T>>)?

    • Current behavior: An error to specify types
    • Other alternatives: [treat impl Trait as arguments in the list, permitting migration]
  • Some concerns about nested impl Trait usage

Open RFCs:


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