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Add an impl of Error on Arc<impl Error>
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#80553
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r? @kennytm (rust-highfive has picked a reviewer for you, use r? to override) |
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I started a stream on Zulip for discussion. |
library/std/src/error.rs
Outdated
@@ -488,6 +489,23 @@ impl<T: Error> Error for Box<T> { | |||
} | |||
} | |||
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#[stable(feature = "arc_error", since = "1.51.0")] | |||
impl<T: Error> Error for Arc<T> { |
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impl<T: Error> Error for Arc<T> { | |
impl<T: Error + ?Sized> Error for Arc<T> { |
unlike Box we should be able to add the ?Sized
bound.
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That would prevent a From
impl for E: Error
in the future, we okay with that? Seems like an inconsistency that would probably bother a lot of people... (not sure this is a good reason to not do it)
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I'm not sure there would be many ?Sized
errors in practice. Could this bound be relaxed (with ?Sized
) at a later date and still be backwards-compatible?
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I mean, it might be that it does no harm if we assume a future specialization feature would allow From
impl for E: Error
in the future.
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we couldn't put a ?Sized
on in the future backwards compatibly. This is a problem with Box
right now. This causes overlap for the impls From<T> for T
and From<E: Error> for Arc<dyn Error + ...>
. It would become ambiguous when converting Arc<dyn Error>
into an Arc<dyn Error>
whether or not you should do a unit conversion or wrap the Arc in another Arc.
As for specialization, I'm not as sure but as far as I know it won't help here. I've looked this up before and my understanding is that this would require rustc to implement the lattice rule, but afaik there are no plans to implement this. That said, I've never had this confirmed by @rust-lang/wg-traits, so this might be on the roadmap even if it's not in the RFC, or I could be misunderstanding the RFC.
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This stuff is extremely nuanced, thankyou for taking the time to work though it all.
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I think ideally we'd want the ?Sized
bound on there. The fact that Box<dyn Error>
, which is a very common pattern, doesn't implement Error
is something we regret. So I think aligning this impl to the one for &'a E: Error + ?Sized
is better than aligning it to Box<E: Error>
.
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Agreed, @derekdreery, could you go ahead and apply this suggestion?
|
cc @rust-lang/project-error-handling |
LGTM |
☔ The latest upstream changes (presumably #81355) made this pull request unmergeable. Please resolve the merge conflicts. |
@rfcbot fcp merge This implements |
Team member @KodrAus has proposed to merge this. The next step is review by the rest of the tagged team members: No concerns currently listed. Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up! See this document for info about what commands tagged team members can give me. |
🔔 This is now entering its final comment period, as per the review above. 🔔 |
The final comment period, with a disposition to merge, as per the review above, is now complete. As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed. The RFC will be merged soon. |
@derekdreery Can you rebase/squash? We generally try to avoid merge commits on branches/PRs. |
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@m-ou-se rebased/squashed. :) |
@bors r+ |
📌 Commit 0d6640a has been approved by |
Rollup of 16 pull requests Successful merges: - rust-lang#75807 (Convert core/num/mod.rs to intra-doc links) - rust-lang#80534 (Use #[doc = include_str!()] in std) - rust-lang#80553 (Add an impl of Error on `Arc<impl Error>`.) - rust-lang#81167 (Make ptr::write const) - rust-lang#81575 (rustdoc: Name fields of `ResolutionFailure::WrongNamespace`) - rust-lang#81713 (Account for associated consts in the "unstable assoc item name colission" lint) - rust-lang#82078 (Make char and u8 methods const) - rust-lang#82087 (Fix ICE caused by suggestion with no code substitutions) - rust-lang#82090 (Do not consider using a semicolon inside of a different-crate macro) - rust-lang#82213 (Slices for vecs) - rust-lang#82214 (Remove redundant to_string calls) - rust-lang#82220 (fix the false 'defined here' messages) - rust-lang#82313 (Update normalize.css to 8.0.1) - rust-lang#82321 (AST: Remove some unnecessary boxes) - rust-lang#82364 (Improve error msgs when found type is deref of expected) - rust-lang#82514 (Update Clippy) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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Package changes: * bump bootstraps to 1.51.0. * adjust patches and cargo checksums as required * 1.51 failed to build natively on 32-bit armv7, there is hope that this is fixed with 1.52. (1.51 can be built with netbsd32 emulation on a aarch64 system). Upsteream changes: Version 1.52.0 (2021-05-06) ============================ Language -------- - [Added the `unsafe_op_in_unsafe_fn` lint, which checks whether the unsafe code in an `unsafe fn` is wrapped in a `unsafe` block.][79208] This lint is allowed by default, and may become a warning or hard error in a future edition. - [You can now cast mutable references to arrays to a pointer of the same type as the element.][81479] Compiler -------- - [Upgraded the default LLVM to LLVM 12.][81451] Added tier 3\* support for the following targets. - [`s390x-unknown-linux-musl`][82166] - [`riscv32gc-unknown-linux-musl` & `riscv64gc-unknown-linux-musl`][82202] - [`powerpc-unknown-openbsd`][82733] \* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [`OsString` now implements `Extend` and `FromIterator`.][82121] - [`cmp::Reverse` now has `#[repr(transparent)]` representation.][81879] - [`Arc<impl Error>` now implements `error::Error`.][80553] - [All integer division and remainder operations are now `const`.][80962] Stabilised APIs ------------- - [`Arguments::as_str`] - [`char::MAX`] - [`char::REPLACEMENT_CHARACTER`] - [`char::UNICODE_VERSION`] - [`char::decode_utf16`] - [`char::from_digit`] - [`char::from_u32_unchecked`] - [`char::from_u32`] - [`slice::partition_point`] - [`str::rsplit_once`] - [`str::split_once`] The following previously stable APIs are now `const`. - [`char::len_utf8`] - [`char::len_utf16`] - [`char::to_ascii_uppercase`] - [`char::to_ascii_lowercase`] - [`char::eq_ignore_ascii_case`] - [`u8::to_ascii_uppercase`] - [`u8::to_ascii_lowercase`] - [`u8::eq_ignore_ascii_case`] Rustdoc ------- - [Rustdoc lints are now treated as a tool lint, meaning that lints are now prefixed with `rustdoc::` (e.g. `#[warn(rustdoc::non_autolinks)]`).][80527] Using the old style is still allowed, and will become a warning in a future release. - [Rustdoc now supports argument files.][82261] - [Rustdoc now generates smart punctuation for documentation.][79423] - [You can now use "task lists" in Rustdoc Markdown.][81766] E.g. ```markdown - [x] Complete - [ ] Todo ``` Misc ---- - [You can now pass multiple filters to tests.][81356] E.g. `cargo test -- foo bar` will run all tests that match `foo` and `bar`. - [Rustup now distributes PDB symbols for the `std` library on Windows, allowing you to see `std` symbols when debugging.][82218] Internal Only ------------- These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools. - [Check the result cache before the DepGraph when ensuring queries][81855] - [Try fast_reject::simplify_type in coherence before doing full check][81744] - [Only store a LocalDefId in some HIR nodes][81611] - [Store HIR attributes in a side table][79519] Compatibility Notes ------------------- - [Cargo build scripts are now forbidden from setting `RUSTC_BOOTSTRAP`.] [cargo/9181] - [Removed support for the `x86_64-rumprun-netbsd` target.][82594] - [Deprecated the `x86_64-sun-solaris` target in favor of `x86_64-pc-solaris`.] [82216] - [Rustdoc now only accepts `,`, ` `, and `\t` as delimiters for specifying languages in code blocks.][78429] - [Rustc now catches more cases of `pub_use_of_private_extern_crate`][80763] - [Changes in how proc macros handle whitespace may lead to panics when used with older `proc-macro-hack` versions. A `cargo update` should be sufficient to fix this in all cases.][84136] [84136]: rust-lang/rust#84136 [80763]: rust-lang/rust#80763 [82166]: rust-lang/rust#82166 [82121]: rust-lang/rust#82121 [81879]: rust-lang/rust#81879 [82261]: rust-lang/rust#82261 [82218]: rust-lang/rust#82218 [82216]: rust-lang/rust#82216 [82202]: rust-lang/rust#82202 [81855]: rust-lang/rust#81855 [81766]: rust-lang/rust#81766 [81744]: rust-lang/rust#81744 [81611]: rust-lang/rust#81611 [81479]: rust-lang/rust#81479 [81451]: rust-lang/rust#81451 [81356]: rust-lang/rust#81356 [80962]: rust-lang/rust#80962 [80553]: rust-lang/rust#80553 [80527]: rust-lang/rust#80527 [79519]: rust-lang/rust#79519 [79423]: rust-lang/rust#79423 [79208]: rust-lang/rust#79208 [78429]: rust-lang/rust#78429 [82733]: rust-lang/rust#82733 [82594]: rust-lang/rust#82594 [cargo/9181]: rust-lang/cargo#9181 [`char::MAX`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.MAX [`char::REPLACEMENT_CHARACTER`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.REPLACEMENT_CHARACTER [`char::UNICODE_VERSION`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.UNICODE_VERSION [`char::decode_utf16`]: https://doc.rust-lang.org/std/primitive.char.html#method.decode_utf16 [`char::from_u32`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32 [`char::from_u32_unchecked`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32_unchecked [`char::from_digit`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_digit [`Peekable::next_if`]: https://doc.rust-lang.org/stable/std/iter/struct.Peekable.html#method.next_if [`Peekable::next_if_eq`]: https://doc.rust-lang.org/stable/std/iter/struct.Peekable.html#method.next_if_eq [`Arguments::as_str`]: https://doc.rust-lang.org/stable/std/fmt/struct.Arguments.html#method.as_str [`str::split_once`]: https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_once [`str::rsplit_once`]: https://doc.rust-lang.org/stable/std/primitive.str.html#method.rsplit_once [`slice::partition_point`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.partition_point [`char::len_utf8`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.len_utf8 [`char::len_utf16`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.len_utf16 [`char::to_ascii_uppercase`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.to_ascii_uppercase [`char::to_ascii_lowercase`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.to_ascii_lowercase [`char::eq_ignore_ascii_case`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.eq_ignore_ascii_case [`u8::to_ascii_uppercase`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_ascii_uppercase [`u8::to_ascii_lowercase`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_ascii_lowercase [`u8::eq_ignore_ascii_case`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.eq_ignore_ascii_case
Pkgsrc changes: * Bump bootstrap kit version to 1.51.0. * Adjust patches as needed. * Update checksum adjustments. * Fix syntax error in commands adjusting libserde_derive for Darwin Upstream changes: Version 1.52.1 (2021-05-10) ============================ This release disables incremental compilation, unless the user has explicitly opted in via the newly added RUSTC_FORCE_INCREMENTAL=1 environment variable. This is due to the widespread, and frequently occuring, breakage encountered by Rust users due to newly enabled incremental verification in 1.52.0. Notably, Rust users **should** upgrade to 1.52.0 or 1.52.1: the bugs that are detected by newly added incremental verification are still present in past stable versions, and are not yet fixed on any channel. These bugs can lead to miscompilation of Rust binaries. These problems only affect incremental builds, so release builds with Cargo should not be affected unless the user has explicitly opted into incremental. Debug and check builds are affected. See [84970] for more details. [84970]: rust-lang/rust#84970 Version 1.52.0 (2021-05-06) ============================ Language -------- - [Added the `unsafe_op_in_unsafe_fn` lint, which checks whether the unsafe code in an `unsafe fn` is wrapped in a `unsafe` block.][79208] This lint is allowed by default, and may become a warning or hard error in a future edition. - [You can now cast mutable references to arrays to a pointer of the same type as the element.][81479] Compiler -------- - [Upgraded the default LLVM to LLVM 12.][81451] Added tier 3\* support for the following targets. - [`s390x-unknown-linux-musl`][82166] - [`riscv32gc-unknown-linux-musl` & `riscv64gc-unknown-linux-musl`][82202] - [`powerpc-unknown-openbsd`][82733] \* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [`OsString` now implements `Extend` and `FromIterator`.][82121] - [`cmp::Reverse` now has `#[repr(transparent)]` representation.][81879] - [`Arc<impl Error>` now implements `error::Error`.][80553] - [All integer division and remainder operations are now `const`.][80962] Stabilised APIs ------------- - [`Arguments::as_str`] - [`char::MAX`] - [`char::REPLACEMENT_CHARACTER`] - [`char::UNICODE_VERSION`] - [`char::decode_utf16`] - [`char::from_digit`] - [`char::from_u32_unchecked`] - [`char::from_u32`] - [`slice::partition_point`] - [`str::rsplit_once`] - [`str::split_once`] The following previously stable APIs are now `const`. - [`char::len_utf8`] - [`char::len_utf16`] - [`char::to_ascii_uppercase`] - [`char::to_ascii_lowercase`] - [`char::eq_ignore_ascii_case`] - [`u8::to_ascii_uppercase`] - [`u8::to_ascii_lowercase`] - [`u8::eq_ignore_ascii_case`] Rustdoc ------- - [Rustdoc lints are now treated as a tool lint, meaning that lints are now prefixed with `rustdoc::` (e.g. `#[warn(rustdoc::non_autolinks)]`).][80527] Using the old style is still allowed, and will become a warning in a future release. - [Rustdoc now supports argument files.][82261] - [Rustdoc now generates smart punctuation for documentation.][79423] - [You can now use "task lists" in Rustdoc Markdown.][81766] E.g. ```markdown - [x] Complete - [ ] Todo ``` Misc ---- - [You can now pass multiple filters to tests.][81356] E.g. `cargo test -- foo bar` will run all tests that match `foo` and `bar`. - [Rustup now distributes PDB symbols for the `std` library on Windows, allowing you to see `std` symbols when debugging.][82218] Internal Only ------------- These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools. - [Check the result cache before the DepGraph when ensuring queries][81855] - [Try fast_reject::simplify_type in coherence before doing full check][81744] - [Only store a LocalDefId in some HIR nodes][81611] - [Store HIR attributes in a side table][79519] Compatibility Notes ------------------- - [Cargo build scripts are now forbidden from setting `RUSTC_BOOTSTRAP`.][cargo/9181] - [Removed support for the `x86_64-rumprun-netbsd` target.][82594] - [Deprecated the `x86_64-sun-solaris` target in favor of `x86_64-pc-solaris`.][82216] - [Rustdoc now only accepts `,`, ` `, and `\t` as delimiters for specifying languages in code blocks.][78429] - [Rustc now catches more cases of `pub_use_of_private_extern_crate`][80763] - [Changes in how proc macros handle whitespace may lead to panics when used with older `proc-macro-hack` versions. A `cargo update` should be sufficient to fix this in all cases.][84136] [84136]: rust-lang/rust#84136 [80763]: rust-lang/rust#80763 [82166]: rust-lang/rust#82166 [82121]: rust-lang/rust#82121 [81879]: rust-lang/rust#81879 [82261]: rust-lang/rust#82261 [82218]: rust-lang/rust#82218 [82216]: rust-lang/rust#82216 [82202]: rust-lang/rust#82202 [81855]: rust-lang/rust#81855 [81766]: rust-lang/rust#81766 [81744]: rust-lang/rust#81744 [81611]: rust-lang/rust#81611 [81479]: rust-lang/rust#81479 [81451]: rust-lang/rust#81451 [81356]: rust-lang/rust#81356 [80962]: rust-lang/rust#80962 [80553]: rust-lang/rust#80553 [80527]: rust-lang/rust#80527 [79519]: rust-lang/rust#79519 [79423]: rust-lang/rust#79423 [79208]: rust-lang/rust#79208 [78429]: rust-lang/rust#78429 [82733]: rust-lang/rust#82733 [82594]: rust-lang/rust#82594 [cargo/9181]: rust-lang/cargo#9181 [`char::MAX`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.MAX [`char::REPLACEMENT_CHARACTER`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.REPLACEMENT_CHARACTER [`char::UNICODE_VERSION`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.UNICODE_VERSION [`char::decode_utf16`]: https://doc.rust-lang.org/std/primitive.char.html#method.decode_utf16 [`char::from_u32`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32 [`char::from_u32_unchecked`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32_unchecked [`char::from_digit`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_digit [`Peekable::next_if`]: https://doc.rust-lang.org/stable/std/iter/struct.Peekable.html#method.next_if [`Peekable::next_if_eq`]: https://doc.rust-lang.org/stable/std/iter/struct.Peekable.html#method.next_if_eq [`Arguments::as_str`]: https://doc.rust-lang.org/stable/std/fmt/struct.Arguments.html#method.as_str [`str::split_once`]: https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_once [`str::rsplit_once`]: https://doc.rust-lang.org/stable/std/primitive.str.html#method.rsplit_once [`slice::partition_point`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.partition_point [`char::len_utf8`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.len_utf8 [`char::len_utf16`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.len_utf16 [`char::to_ascii_uppercase`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.to_ascii_uppercase [`char::to_ascii_lowercase`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.to_ascii_lowercase [`char::eq_ignore_ascii_case`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.eq_ignore_ascii_case [`u8::to_ascii_uppercase`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_ascii_uppercase [`u8::to_ascii_lowercase`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_ascii_lowercase [`u8::eq_ignore_ascii_case`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.eq_ignore_ascii_case
Display
already exists so this should be a non-controversial change (famous last words).Would have to be insta-stable.