Tracking issue for impl Trait in const and static items and let bindings
#63065
Labels
A-impl-trait
Area: `impl Trait`. Universally / existentially quantified anonymous types with static dispatch.
B-RFC-approved
Blocker: Approved by a merged RFC but not yet implemented.
B-unstable
Blocker: Implemented in the nightly compiler and unstable.
C-tracking-issue
Category: A tracking issue for an RFC or an unstable feature.
F-impl_trait_in_bindings
`#![feature(impl_trait_in_bindings)]`
requires-nightly
This issue requires a nightly compiler in some way.
S-tracking-impl-incomplete
Status: The implementation is incomplete.
T-lang
Relevant to the language team, which will review and decide on the PR/issue.
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Centril
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B-RFC-approved
This was referenced Jul 28, 2019
Centril
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F-impl_trait_in_bindings
Centril
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…varkor Update `impl Trait` gate issues cc rust-lang#63065 cc rust-lang#63063 r? @varkor cc @alexreg
strohel
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The existing issue rust-lang#34511 has been closed and replaced by meta-issue rust-lang#63066. The concrete part of the new meta-issue for this feature should be rust-lang#63065.
This was referenced Apr 10, 2020
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=== stdout === === stderr === warning: the feature `impl_trait_in_bindings` is incomplete and may not be safe to use and/or cause compiler crashes --> <anon>:1:12 | 1 | #![feature(impl_trait_in_bindings)] | ^^^^^^^^^^^^^^^^^^^^^^ | = note: `#[warn(incomplete_features)]` on by default = note: see issue #63065 <rust-lang/rust#63065> for more information warning: function is never used: `foo` --> <anon>:16:8 | 16 | fn foo<T: Trait<Assoc=u32>>() { | ^^^ | = note: `#[warn(dead_code)]` on by default warning: 2 warnings emitted ==============
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=== stdout === === stderr === /home/runner/work/glacier/glacier/ices/75962.sh: line 3: impl: command not found warning: the feature `impl_trait_in_bindings` is incomplete and may not be safe to use and/or cause compiler crashes --> <anon>:3:12 | 3 | #![feature(impl_trait_in_bindings)] | ^^^^^^^^^^^^^^^^^^^^^^ | = note: `#[warn(incomplete_features)]` on by default = note: see issue #63065 <rust-lang/rust#63065> for more information warning: function is never used: `foo` --> <anon>:29:8 | 29 | fn foo<T: Trait<Assoc=u32>>() { | ^^^ | = note: `#[warn(dead_code)]` on by default warning: 2 warnings emitted ==============
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=== stdout === === stderr === warning: the feature `impl_trait_in_bindings` is incomplete and may not be safe to use and/or cause compiler crashes --> /home/runner/work/glacier/glacier/ices/78721.rs:1:12 | 1 | #![feature(impl_trait_in_bindings)] | ^^^^^^^^^^^^^^^^^^^^^^ | = note: `#[warn(incomplete_features)]` on by default = note: see issue #63065 <rust-lang/rust#63065> for more information error: `async` blocks are not allowed in constants --> /home/runner/work/glacier/glacier/ices/78721.rs:5:57 | 5 | let f: impl core::future::Future<Output = u8> = async { 1 }; | ^^^^^^^^^^^ error[E0493]: destructors cannot be evaluated at compile-time --> /home/runner/work/glacier/glacier/ices/78721.rs:5:13 | 5 | let f: impl core::future::Future<Output = u8> = async { 1 }; | ^ constants cannot evaluate destructors 6 | 1 7 | }], | - value is dropped here error: aborting due to 2 previous errors; 1 warning emitted For more information about this error, try `rustc --explain E0493`. ==============
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=== stdout === === stderr === warning: the feature `impl_trait_in_bindings` is incomplete and may not be safe to use and/or cause compiler crashes --> /home/runner/work/glacier/glacier/ices/78722.rs:2:12 | 2 | #![feature(impl_trait_in_bindings)] | ^^^^^^^^^^^^^^^^^^^^^^ | = note: `#[warn(incomplete_features)]` on by default = note: see issue #63065 <rust-lang/rust#63065> for more information error: `async` blocks are not allowed in constants --> /home/runner/work/glacier/glacier/ices/78722.rs:11:20 | 11 | let f: F = async { 1 }; | ^^^^^^^^^^^ error[E0493]: destructors cannot be evaluated at compile-time --> /home/runner/work/glacier/glacier/ices/78722.rs:11:13 | 11 | let f: F = async { 1 }; | ^ constants cannot evaluate destructors 12 | 1 13 | }], | - value is dropped here error: aborting due to 2 previous errors; 1 warning emitted For more information about this error, try `rustc --explain E0493`. ==============
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What's the status on this now? Is it ready to be stabilised? |
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=== stdout === === stderr === error[E0658]: `impl Trait` in type aliases is unstable --> /home/runner/work/glacier/glacier/ices/53092.rs:21:18 | 21 | type Bug<T, U> = impl Fn(T) -> U + Copy; | ^^^^^^^^^^^^^^^^^^^^^^ | = note: see issue #63063 <rust-lang/rust#63063> for more information = help: add `#![feature(min_type_alias_impl_trait)]` to the crate attributes to enable warning: the feature `type_alias_impl_trait` is incomplete and may not be safe to use and/or cause compiler crashes --> /home/runner/work/glacier/glacier/ices/53092.rs:3:12 | 3 | #![feature(type_alias_impl_trait)] | ^^^^^^^^^^^^^^^^^^^^^ | = note: `#[warn(incomplete_features)]` on by default = note: see issue #63063 <rust-lang/rust#63063> for more information error[E0658]: type alias impl trait is not permitted here --> /home/runner/work/glacier/glacier/ices/53092.rs:23:32 | 23 | const CONST_BUG: Bug<u8, ()> = transmute(|_: u8| ()); | ^^^^^^^^^^^^^^^^^^^^^ | = note: see issue #63065 <rust-lang/rust#63065> for more information = help: add `#![feature(impl_trait_in_bindings)]` to the crate attributes to enable error: concrete type differs from previous defining opaque type use --> /home/runner/work/glacier/glacier/ices/53092.rs:25:1 | 25 | fn make_bug<T, U: From<T>>() -> Bug<T, U> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `[type error]`, got `[closure@/home/runner/work/glacier/glacier/ices/53092.rs:26:5: 26:17]` | note: previous use here --> /home/runner/work/glacier/glacier/ices/53092.rs:23:1 | 23 | const CONST_BUG: Bug<u8, ()> = transmute(|_: u8| ()); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: aborting due to 3 previous errors; 1 warning emitted For more information about this error, try `rustc --explain E0658`. ==============
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=== stdout === === stderr === error[E0557]: feature has been removed --> /home/runner/work/glacier/glacier/ices/53092.rs:1:12 | 1 | #![feature(const_fn)] | ^^^^^^^^ feature has been removed | = note: split into finer-grained feature gates warning: the feature `impl_trait_in_bindings` is incomplete and may not be safe to use and/or cause compiler crashes --> /home/runner/work/glacier/glacier/ices/53092.rs:3:12 | 3 | #![feature(impl_trait_in_bindings)] | ^^^^^^^^^^^^^^^^^^^^^^ | = note: `#[warn(incomplete_features)]` on by default = note: see issue #63065 <rust-lang/rust#63065> for more information warning: the feature `type_alias_impl_trait` is incomplete and may not be safe to use and/or cause compiler crashes --> /home/runner/work/glacier/glacier/ices/53092.rs:5:12 | 5 | #![feature(type_alias_impl_trait)] | ^^^^^^^^^^^^^^^^^^^^^ | = note: see issue #63063 <rust-lang/rust#63063> for more information error: aborting due to previous error; 2 warnings emitted For more information about this error, try `rustc --explain E0557`. ==============
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=== stdout === === stderr === warning: the feature `impl_trait_in_bindings` is incomplete and may not be safe to use and/or cause compiler crashes --> /home/runner/work/glacier/glacier/ices/85113.rs:2:12 | 2 | #![feature(impl_trait_in_bindings)] | ^^^^^^^^^^^^^^^^^^^^^^ | = note: `#[warn(incomplete_features)]` on by default = note: see issue #63065 <rust-lang/rust#63065> for more information error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds --> /home/runner/work/glacier/glacier/ices/85113.rs:4:29 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^^^^^^^^^^^^^^^^^^^ | note: hidden type `&'<empty> str` captures lifetime smaller than the function body --> /home/runner/work/glacier/glacier/ices/85113.rs:4:29 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^^^^^^^^^^^^^^^^^^^ error[E0477]: the type `&'<empty> str` does not fulfill the required lifetime --> /home/runner/work/glacier/glacier/ices/85113.rs:4:29 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^^^^^^^^^^^^^^^^^^^ | note: type must outlive the lifetime `'a` as defined on the item at 4:23 --> /home/runner/work/glacier/glacier/ices/85113.rs:4:23 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^ error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements --> /home/runner/work/glacier/glacier/ices/85113.rs:4:29 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^^^^^^^^^^^^^^^^^^^ | = note: first, the lifetime cannot outlive the empty lifetime... note: ...but the lifetime must also be valid for the lifetime `'a` as defined on the item at 4:23... --> /home/runner/work/glacier/glacier/ices/85113.rs:4:23 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^ note: ...so that the types are compatible --> /home/runner/work/glacier/glacier/ices/85113.rs:4:29 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^^^^^^^^^^^^^^^^^^^ = note: expected `Output<'a>` found `Output<'_>` error: aborting due to 3 previous errors; 1 warning emitted Some errors have detailed explanations: E0477, E0495, E0700. For more information about an error, try `rustc --explain E0477`. ==============
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=== stdout === === stderr === warning: the feature `impl_trait_in_bindings` is incomplete and may not be safe to use and/or cause compiler crashes --> /home/runner/work/glacier/glacier/ices/85113.rs:2:12 | 2 | #![feature(impl_trait_in_bindings)] | ^^^^^^^^^^^^^^^^^^^^^^ | = note: `#[warn(incomplete_features)]` on by default = note: see issue #63065 <rust-lang/rust#63065> for more information error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds --> /home/runner/work/glacier/glacier/ices/85113.rs:4:29 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^^^^^^^^^^^^^^^^^^^ | note: hidden type `&'<empty> str` captures lifetime smaller than the function body --> /home/runner/work/glacier/glacier/ices/85113.rs:4:29 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^^^^^^^^^^^^^^^^^^^ error[E0477]: the type `&'<empty> str` does not fulfill the required lifetime --> /home/runner/work/glacier/glacier/ices/85113.rs:4:29 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^^^^^^^^^^^^^^^^^^^ | note: type must outlive the lifetime `'a` as defined on the item at 4:23 --> /home/runner/work/glacier/glacier/ices/85113.rs:4:23 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^ error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements --> /home/runner/work/glacier/glacier/ices/85113.rs:4:29 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^^^^^^^^^^^^^^^^^^^ | = note: first, the lifetime cannot outlive the empty lifetime... note: ...but the lifetime must also be valid for the lifetime `'a` as defined on the item at 4:23... --> /home/runner/work/glacier/glacier/ices/85113.rs:4:23 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^ note: ...so that the types are compatible --> /home/runner/work/glacier/glacier/ices/85113.rs:4:29 | 4 | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a; | ^^^^^^^^^^^^^^^^^^^^ = note: expected `Output<'a>` found `Output<'_>` error: aborting due to 3 previous errors; 1 warning emitted Some errors have detailed explanations: E0477, E0495, E0700. For more information about an error, try `rustc --explain E0477`. ============== Co-authored-by: rustbot <rustbot@users.noreply.github.com>
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The implementation was removed as part of #86729 and the corresponding checkbox should be unchecked. |
joshtriplett
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S-tracking-impl-incomplete
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Pinging, is there any progress on this feature? |
8 tasks
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Hopefully there will be soon, as it was the cleanest way for me to solve an issue just now. |
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As provided for by rust-lang/rfcs#2071, this is a tracking issue for
impl Traitin:constitemsstaticitemsletbindingsSteps:
Unresolved questions:
letbindings be recast more generally to be about coercions? This would allowfoo as impl Debugandfoo: impl Debugas well.Blocking issues:
Incomplete. Search the
F-impl_trait_in_bindingsissue.impl_trait_in_bindingsis a breaking change #83021impl_trait_in_bindingsand pick-constraint region bounds #61773The text was updated successfully, but these errors were encountered: