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Fix ambiguous cases of multiple & in elided self lifetimes #117967
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r? @cjgillot (rustbot has picked a reviewer for you, use r? to override) |
@cjgillot hello, I didn't know rustbot would assign a reviewer for a draft PR. This isn't yet ready. |
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Btw, you can use |
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I've now marked this as ready for review. Per discussion on #117715, this will need a crater run. It's possible that we want to make the tests a bit more thorough before merging, but it would be good to initially get feedback on the approach (and maybe a crater run to find out if it's doomed) |
let's do a crater run. I am still unsure about the exact behavior we want and probably have to look into this myself to figure it out 🤔 but for now @bors try |
…r=<try> Fix lifetime elision ```rust struct Concrete(u32); impl Concrete { fn m(self: &Box<Self>) -> &u32 { &self.0 } } ``` resulted in a confusing error. ```rust impl Concrete { fn n(self: &Box<&Self>) -> &u32 { &self.0 } } ``` resulted in no error or warning, despite apparent ambiguity over the elided lifetime. Fixes rust-lang#117715
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r? @lcnr |
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. This will be merged soon. |
@lcnr: Heads-up that FCP completed on this, so this is good to go forward as far as lang is concerned. |
missed that this finished FCP already. Thanks for the good work @adetaylor and thanks for sticking with it for this long! @bors r+ rollup=never |
@bors r+ rollup=never |
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Finished benchmarking commit (5753b30): comparison URL. Overall result: ✅ improvements - no action needed@rustbot label: -perf-regression Instruction countThis is a highly reliable metric that was used to determine the overall result at the top of this comment.
Max RSS (memory usage)Results (primary 1.8%)This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesResults (secondary -2.5%)This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 767.488s -> 768.843s (0.18%) |
Fix ambiguous cases of multiple & in elided self lifetimes This change proposes simpler rules to identify the lifetime on `self` parameters which may be used to elide a return type lifetime. ## The old rules (copied from [this comment](rust-lang/rust#117967 (comment))) Most of the code can be found in [late.rs](https://doc.rust-lang.org/stable/nightly-rustc/src/rustc_resolve/late.rs.html) and acts on AST types. The function [resolve_fn_params](https://doc.rust-lang.org/stable/nightly-rustc/src/rustc_resolve/late.rs.html#2006), in the success case, returns a single lifetime which can be used to elide the lifetime of return types. Here's how: * If the first parameter is called self then we search that parameter using "`self` search rules", below * If no unique applicable lifetime was found, search all other parameters using "regular parameter search rules", below (In practice the code does extra work to assemble good diagnostic information, so it's not quite laid out like the above.) ### `self` search rules This is primarily handled in [find_lifetime_for_self](https://doc.rust-lang.org/stable/nightly-rustc/src/rustc_resolve/late.rs.html#2118) , and is described slightly [here](rust-lang/rust#117715 (comment)) already. The code: 1. Recursively walks the type of the `self` parameter (there's some complexity about resolving various special cases, but it's essentially just walking the type as far as I can see) 2. Each time we find a reference anywhere in the type, if the **direct** referent is `Self` (either spelled `Self` or by some alias resolution which I don't fully understand), then we'll add that to a set of candidate lifetimes 3. If there's exactly one such unique lifetime candidate found, we return this lifetime. ### Regular parameter search rules 1. Find all the lifetimes in each parameter, including implicit, explicit etc. 2. If there's exactly one parameter containing lifetimes, and if that parameter contains exactly one (unique) lifetime, *and if we didn't find a `self` lifetime parameter already*, we'll return this lifetime. ## The new rules There are no changes to the "regular parameter search rules" or to the overall flow, only to the `self` search rules which are now: 1. Recursively walks the type of the `self` parameter, searching for lifetimes of reference types whose referent **contains** `Self`.[^1] 2. Keep a record of: * Whether 0, 1 or n unique lifetimes are found on references encountered during the walk 4. If no lifetime was found, we don't return a lifetime. (This means other parameters' lifetimes may be used for return type lifetime elision). 5. If there's one lifetime found, we return the lifetime. 6. If multiple lifetimes were found, we abort elision entirely (other parameters' lifetimes won't be used). [^1]: this prevents us from considering lifetimes from inside of the self-type ## Examples that were accepted before and will now be rejected ```rust fn a(self: &Box<&Self>) -> &u32 fn b(self: &Pin<&mut Self>) -> &String fn c(self: &mut &Self) -> Option<&Self> fn d(self: &mut &Box<Self>, arg: &usize) -> &usize // previously used the lt from arg ``` ### Examples that change the elided lifetime ```rust fn e(self: &mut Box<Self>, arg: &usize) -> &usize // ^ new ^ previous ``` ## Examples that were rejected before and will now be accepted ```rust fn f(self: &Box<Self>) -> &u32 ``` --- *edit: old PR description:* ```rust struct Concrete(u32); impl Concrete { fn m(self: &Box<Self>) -> &u32 { &self.0 } } ``` resulted in a confusing error. ```rust impl Concrete { fn n(self: &Box<&Self>) -> &u32 { &self.0 } } ``` resulted in no error or warning, despite apparent ambiguity over the elided lifetime. Fixes rust-lang/rust#117715
Fix ambiguous cases of multiple & in elided self lifetimes This change proposes simpler rules to identify the lifetime on `self` parameters which may be used to elide a return type lifetime. ## The old rules (copied from [this comment](rust-lang/rust#117967 (comment))) Most of the code can be found in [late.rs](https://doc.rust-lang.org/stable/nightly-rustc/src/rustc_resolve/late.rs.html) and acts on AST types. The function [resolve_fn_params](https://doc.rust-lang.org/stable/nightly-rustc/src/rustc_resolve/late.rs.html#2006), in the success case, returns a single lifetime which can be used to elide the lifetime of return types. Here's how: * If the first parameter is called self then we search that parameter using "`self` search rules", below * If no unique applicable lifetime was found, search all other parameters using "regular parameter search rules", below (In practice the code does extra work to assemble good diagnostic information, so it's not quite laid out like the above.) ### `self` search rules This is primarily handled in [find_lifetime_for_self](https://doc.rust-lang.org/stable/nightly-rustc/src/rustc_resolve/late.rs.html#2118) , and is described slightly [here](rust-lang/rust#117715 (comment)) already. The code: 1. Recursively walks the type of the `self` parameter (there's some complexity about resolving various special cases, but it's essentially just walking the type as far as I can see) 2. Each time we find a reference anywhere in the type, if the **direct** referent is `Self` (either spelled `Self` or by some alias resolution which I don't fully understand), then we'll add that to a set of candidate lifetimes 3. If there's exactly one such unique lifetime candidate found, we return this lifetime. ### Regular parameter search rules 1. Find all the lifetimes in each parameter, including implicit, explicit etc. 2. If there's exactly one parameter containing lifetimes, and if that parameter contains exactly one (unique) lifetime, *and if we didn't find a `self` lifetime parameter already*, we'll return this lifetime. ## The new rules There are no changes to the "regular parameter search rules" or to the overall flow, only to the `self` search rules which are now: 1. Recursively walks the type of the `self` parameter, searching for lifetimes of reference types whose referent **contains** `Self`.[^1] 2. Keep a record of: * Whether 0, 1 or n unique lifetimes are found on references encountered during the walk 4. If no lifetime was found, we don't return a lifetime. (This means other parameters' lifetimes may be used for return type lifetime elision). 5. If there's one lifetime found, we return the lifetime. 6. If multiple lifetimes were found, we abort elision entirely (other parameters' lifetimes won't be used). [^1]: this prevents us from considering lifetimes from inside of the self-type ## Examples that were accepted before and will now be rejected ```rust fn a(self: &Box<&Self>) -> &u32 fn b(self: &Pin<&mut Self>) -> &String fn c(self: &mut &Self) -> Option<&Self> fn d(self: &mut &Box<Self>, arg: &usize) -> &usize // previously used the lt from arg ``` ### Examples that change the elided lifetime ```rust fn e(self: &mut Box<Self>, arg: &usize) -> &usize // ^ new ^ previous ``` ## Examples that were rejected before and will now be accepted ```rust fn f(self: &Box<Self>) -> &u32 ``` --- *edit: old PR description:* ```rust struct Concrete(u32); impl Concrete { fn m(self: &Box<Self>) -> &u32 { &self.0 } } ``` resulted in a confusing error. ```rust impl Concrete { fn n(self: &Box<&Self>) -> &u32 { &self.0 } } ``` resulted in no error or warning, despite apparent ambiguity over the elided lifetime. Fixes rust-lang/rust#117715
This MR contains the following updates: | Package | Update | Change | |---|---|---| | [rust](https://github.com/rust-lang/rust) | minor | `1.80.1` -> `1.81.0` | MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot). **Proposed changes to behavior should be submitted there as MRs.** --- ### Release Notes <details> <summary>rust-lang/rust (rust)</summary> ### [`v1.81.0`](https://github.com/rust-lang/rust/blob/HEAD/RELEASES.md#Version-1810-2024-09-05) [Compare Source](rust-lang/rust@1.80.1...1.81.0) \========================== <a id="1.81.0-Language"></a> ## Language - [Abort on uncaught panics in `extern "C"` functions.](rust-lang/rust#116088) - [Fix ambiguous cases of multiple `&` in elided self lifetimes.](rust-lang/rust#117967) - [Stabilize `#[expect]` for lints (RFC 2383),](rust-lang/rust#120924) like `#[allow]` with a warning if the lint is *not* fulfilled. - [Change method resolution to constrain hidden types instead of rejecting method candidates.](rust-lang/rust#123962) - [Bump `elided_lifetimes_in_associated_constant` to deny.](rust-lang/rust#124211) - [`offset_from`: always allow pointers to point to the same address.](rust-lang/rust#124921) - [Allow constraining opaque types during subtyping in the trait system.](rust-lang/rust#125447) - [Allow constraining opaque types during various unsizing casts.](rust-lang/rust#125610) - [Deny keyword lifetimes pre-expansion.](rust-lang/rust#126762) <a id="1.81.0-Compiler"></a> ## Compiler - [Make casts of pointers to trait objects stricter.](rust-lang/rust#120248) - [Check alias args for well-formedness even if they have escaping bound vars.](rust-lang/rust#123737) - [Deprecate no-op codegen option `-Cinline-threshold=...`.](rust-lang/rust#124712) - [Re-implement a type-size based limit.](rust-lang/rust#125507) - [Properly account for alignment in `transmute` size checks.](rust-lang/rust#125740) - [Remove the `box_pointers` lint.](rust-lang/rust#126018) - [Ensure the interpreter checks bool/char for validity when they are used in a cast.](rust-lang/rust#126265) - [Improve coverage instrumentation for functions containing nested items.](rust-lang/rust#127199) - Target changes: - [Add Tier 3 `no_std` Xtensa targets:](rust-lang/rust#125141) `xtensa-esp32-none-elf`, `xtensa-esp32s2-none-elf`, `xtensa-esp32s3-none-elf` - [Add Tier 3 `std` Xtensa targets:](rust-lang/rust#126380) `xtensa-esp32-espidf`, `xtensa-esp32s2-espidf`, `xtensa-esp32s3-espidf` - [Add Tier 3 i686 Redox OS target:](rust-lang/rust#126192) `i686-unknown-redox` - [Promote `arm64ec-pc-windows-msvc` to Tier 2.](rust-lang/rust#126039) - [Promote `loongarch64-unknown-linux-musl` to Tier 2 with host tools.](rust-lang/rust#126298) - [Enable full tools and profiler for LoongArch Linux targets.](rust-lang/rust#127078) - [Unconditionally warn on usage of `wasm32-wasi`.](rust-lang/rust#126662) (see compatibility note below) - Refer to Rust's \[platform support page]\[platform-support-doc] for more information on Rust's tiered platform support. <a id="1.81.0-Libraries"></a> ## Libraries - [Split core's `PanicInfo` and std's `PanicInfo`.](rust-lang/rust#115974) (see compatibility note below) - [Generalize `{Rc,Arc}::make_mut()` to unsized types.](rust-lang/rust#116113) - [Replace sort implementations with stable `driftsort` and unstable `ipnsort`.](rust-lang/rust#124032) All `slice::sort*` and `slice::select_nth*` methods are expected to see significant performance improvements. See the [research project](https://github.com/Voultapher/sort-research-rs) for more details. - [Document behavior of `create_dir_all` with respect to empty paths.](rust-lang/rust#125112) - [Fix interleaved output in the default panic hook when multiple threads panic simultaneously.](rust-lang/rust#127397) <a id="1.81.0-Stabilized-APIs"></a> ## Stabilized APIs - [`core::error`](https://doc.rust-lang.org/stable/core/error/index.html) - [`hint::assert_unchecked`](https://doc.rust-lang.org/stable/core/hint/fn.assert_unchecked.html) - [`fs::exists`](https://doc.rust-lang.org/stable/std/fs/fn.exists.html) - [`AtomicBool::fetch_not`](https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicBool.html#method.fetch_not) - [`Duration::abs_diff`](https://doc.rust-lang.org/stable/core/time/struct.Duration.html#method.abs_diff) - [`IoSlice::advance`](https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance) - [`IoSlice::advance_slices`](https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance_slices) - [`IoSliceMut::advance`](https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance) - [`IoSliceMut::advance_slices`](https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance_slices) - [`PanicHookInfo`](https://doc.rust-lang.org/stable/std/panic/struct.PanicHookInfo.html) - [`PanicInfo::message`](https://doc.rust-lang.org/stable/core/panic/struct.PanicInfo.html#method.message) - [`PanicMessage`](https://doc.rust-lang.org/stable/core/panic/struct.PanicMessage.html) These APIs are now stable in const contexts: - [`char::from_u32_unchecked`](https://doc.rust-lang.org/stable/core/char/fn.from_u32\_unchecked.html) (function) - [`char::from_u32_unchecked`](https://doc.rust-lang.org/stable/core/primitive.char.html#method.from_u32\_unchecked) (method) - [`CStr::count_bytes`](https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes) - [`CStr::from_ptr`](https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.from_ptr) <a id="1.81.0-Cargo"></a> ## Cargo - [Generated `.cargo_vcs_info.json` is always included, even when `--allow-dirty` is passed.](rust-lang/cargo#13960) - [Disallow `package.license-file` and `package.readme` pointing to non-existent files during packaging.](rust-lang/cargo#13921) - [Disallow passing `--release`/`--debug` flag along with the `--profile` flag.](rust-lang/cargo#13971) - [Remove `lib.plugin` key support in `Cargo.toml`. Rust plugin support has been deprecated for four years and was removed in 1.75.0.](rust-lang/cargo#13902) <a id="1.81.0-Compatibility-Notes"></a> ## Compatibility Notes - Usage of the `wasm32-wasi` target will now issue a compiler warning and request users switch to the `wasm32-wasip1` target instead. Both targets are the same, `wasm32-wasi` is only being renamed, and this [change to the WASI target](https://blog.rust-lang.org/2024/04/09/updates-to-rusts-wasi-targets.html) is being done to enable removing `wasm32-wasi` in January 2025. - We have renamed `std::panic::PanicInfo` to `std::panic::PanicHookInfo`. The old name will continue to work as an alias, but will result in a deprecation warning starting in Rust 1.82.0. `core::panic::PanicInfo` will remain unchanged, however, as this is now a *different type*. The reason is that these types have different roles: `std::panic::PanicHookInfo` is the argument to the [panic hook](https://doc.rust-lang.org/stable/std/panic/fn.set_hook.html) in std context (where panics can have an arbitrary payload), while `core::panic::PanicInfo` is the argument to the [`#[panic_handler]`](https://doc.rust-lang.org/nomicon/panic-handler.html) in no_std context (where panics always carry a formatted *message*). Separating these types allows us to add more useful methods to these types, such as `std::panic::PanicHookInfo::payload_as_str()` and `core::panic::PanicInfo::message()`. - The new sort implementations may panic if a type's implementation of [`Ord`](https://doc.rust-lang.org/std/cmp/trait.Ord.html) (or the given comparison function) does not implement a [total order](https://en.wikipedia.org/wiki/Total_order) as the trait requires. `Ord`'s supertraits (`PartialOrd`, `Eq`, and `PartialEq`) must also be consistent. The previous implementations would not "notice" any problem, but the new implementations have a good chance of detecting inconsistencies, throwing a panic rather than returning knowingly unsorted data. - [In very rare cases, a change in the internal evaluation order of the trait solver may result in new fatal overflow errors.](rust-lang/rust#126128) <a id="1.81.0-Internal-Changes"></a> ## Internal Changes These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Add a Rust-for Linux `auto` CI job to check kernel builds.](rust-lang/rust#125209) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this MR and you won't be reminded about this update again. --- - [ ] <!-- rebase-check -->If you want to rebase/retry this MR, check this box --- This MR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate). <!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNy40NDAuNyIsInVwZGF0ZWRJblZlciI6IjM3LjQ0MC43IiwidGFyZ2V0QnJhbmNoIjoibWFpbiIsImxhYmVscyI6WyJSZW5vdmF0ZSBCb3QiXX0=-->
Pkgsrc changes: * Adapt patches, apply to new vendored crates where needed. * Back-port rust pull request 130110, "make dist vendoring configurable" * Disable "dist vendoring", otherwise cargo would try to access the network during the build phase. Upstream changes: Version 1.81.0 (2024-09-05) ========================== Language -------- - [Abort on uncaught panics in `extern "C"` functions.] (rust-lang/rust#116088) - [Fix ambiguous cases of multiple `&` in elided self lifetimes.] (rust-lang/rust#117967) - [Stabilize `#[expect]` for lints (RFC 2383),] (rust-lang/rust#120924) like `#[allow]` with a warning if the lint is _not_ fulfilled. - [Change method resolution to constrain hidden types instead of rejecting method candidates.] (rust-lang/rust#123962) - [Bump `elided_lifetimes_in_associated_constant` to deny.] (rust-lang/rust#124211) - [`offset_from`: always allow pointers to point to the same address.] (rust-lang/rust#124921) - [Allow constraining opaque types during subtyping in the trait system.] (rust-lang/rust#125447) - [Allow constraining opaque types during various unsizing casts.] (rust-lang/rust#125610) - [Deny keyword lifetimes pre-expansion.] (rust-lang/rust#126762) Compiler -------- - [Make casts of pointers to trait objects stricter.] (rust-lang/rust#120248) - [Check alias args for well-formedness even if they have escaping bound vars.] (rust-lang/rust#123737) - [Deprecate no-op codegen option `-Cinline-threshold=...`.] (rust-lang/rust#124712) - [Re-implement a type-size based limit.] (rust-lang/rust#125507) - [Properly account for alignment in `transmute` size checks.] (rust-lang/rust#125740) - [Remove the `box_pointers` lint.] (rust-lang/rust#126018) - [Ensure the interpreter checks bool/char for validity when they are used in a cast.] (rust-lang/rust#126265) - [Improve coverage instrumentation for functions containing nested items.] (rust-lang/rust#127199) - Target changes: - [Add Tier 3 `no_std` Xtensa targets:] (rust-lang/rust#125141) `xtensa-esp32-none-elf`, `xtensa-esp32s2-none-elf`, `xtensa-esp32s3-none-elf` - [Add Tier 3 `std` Xtensa targets:] (rust-lang/rust#126380) `xtensa-esp32-espidf`, `xtensa-esp32s2-espidf`, `xtensa-esp32s3-espidf` - [Add Tier 3 i686 Redox OS target:] (rust-lang/rust#126192) `i686-unknown-redox` - [Promote `arm64ec-pc-windows-msvc` to Tier 2.] (rust-lang/rust#126039) - [Promote `wasm32-wasip2` to Tier 2.] (rust-lang/rust#126967) - [Promote `loongarch64-unknown-linux-musl` to Tier 2 with host tools.] (rust-lang/rust#126298) - [Enable full tools and profiler for LoongArch Linux targets.] (rust-lang/rust#127078) - [Unconditionally warn on usage of `wasm32-wasi`.] (rust-lang/rust#126662) (see compatibility note below) - Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Split core's `PanicInfo` and std's `PanicInfo`.] (rust-lang/rust#115974) (see compatibility note below) - [Generalize `{Rc,Arc}::make_mut()` to unsized types.] (rust-lang/rust#116113) - [Replace sort implementations with stable `driftsort` and unstable `ipnsort`.] (rust-lang/rust#124032) All `slice::sort*` and `slice::select_nth*` methods are expected to see significant performance improvements. See the [research project] (https://github.com/Voultapher/sort-research-rs) for more details. - [Document behavior of `create_dir_all` with respect to empty paths.] (rust-lang/rust#125112) - [Fix interleaved output in the default panic hook when multiple threads panic simultaneously.] (rust-lang/rust#127397) - Fix `Command`'s batch files argument escaping not working when file name has trailing whitespace or periods (CVE-2024-43402). Stabilized APIs --------------- - [`core::error`] (https://doc.rust-lang.org/stable/core/error/index.html) - [`hint::assert_unchecked`] (https://doc.rust-lang.org/stable/core/hint/fn.assert_unchecked.html) - [`fs::exists`] (https://doc.rust-lang.org/stable/std/fs/fn.exists.html) - [`AtomicBool::fetch_not`] (https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicBool.html#method.fetch_not) - [`Duration::abs_diff`] (https://doc.rust-lang.org/stable/core/time/struct.Duration.html#method.abs_diff) - [`IoSlice::advance`] (https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance) - [`IoSlice::advance_slices`] (https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance_slices) - [`IoSliceMut::advance`] (https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance) - [`IoSliceMut::advance_slices`] (https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance_slices) - [`PanicHookInfo`] (https://doc.rust-lang.org/stable/std/panic/struct.PanicHookInfo.html) - [`PanicInfo::message`] (https://doc.rust-lang.org/stable/core/panic/struct.PanicInfo.html#method.message) - [`PanicMessage`] (https://doc.rust-lang.org/stable/core/panic/struct.PanicMessage.html) These APIs are now stable in const contexts: - [`char::from_u32_unchecked`] (https://doc.rust-lang.org/stable/core/char/fn.from_u32_unchecked.html) (function) - [`char::from_u32_unchecked`] (https://doc.rust-lang.org/stable/core/primitive.char.html#method.from_u32_unchecked) (method) - [`CStr::count_bytes`] (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes) - [`CStr::from_ptr`] (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.from_ptr) Cargo ----- - [Generated `.cargo_vcs_info.json` is always included, even when `--allow-dirty` is passed.] (rust-lang/cargo#13960) - [Disallow `package.license-file` and `package.readme` pointing to non-existent files during packaging.] (rust-lang/cargo#13921) - [Disallow passing `--release`/`--debug` flag along with the `--profile` flag.] (rust-lang/cargo#13971) - [Remove `lib.plugin` key support in `Cargo.toml`. Rust plugin support has been deprecated for four years and was removed in 1.75.0.] (rust-lang/cargo#13902) Compatibility Notes ------------------- * Usage of the `wasm32-wasi` target will now issue a compiler warning and request users switch to the `wasm32-wasip1` target instead. Both targets are the same, `wasm32-wasi` is only being renamed, and this [change to the WASI target] (https://blog.rust-lang.org/2024/04/09/updates-to-rusts-wasi-targets.html) is being done to enable removing `wasm32-wasi` in January 2025. * We have renamed `std::panic::PanicInfo` to `std::panic::PanicHookInfo`. The old name will continue to work as an alias, but will result in a deprecation warning starting in Rust 1.82.0. `core::panic::PanicInfo` will remain unchanged, however, as this is now a *different type*. The reason is that these types have different roles: `std::panic::PanicHookInfo` is the argument to the [panic hook](https://doc.rust-lang.org/stable/std/panic/fn.set_hook.html) in std context (where panics can have an arbitrary payload), while `core::panic::PanicInfo` is the argument to the [`#[panic_handler]`](https://doc.rust-lang.org/nomicon/panic-handler.html) in no_std context (where panics always carry a formatted *message*). Separating these types allows us to add more useful methods to these types, such as `std::panic::PanicHookInfo::payload_as_str()` and `core::panic::PanicInfo::message()`. * The new sort implementations may panic if a type's implementation of [`Ord`](https://doc.rust-lang.org/std/cmp/trait.Ord.html) (or the given comparison function) does not implement a [total order](https://en.wikipedia.org/wiki/Total_order) as the trait requires. `Ord`'s supertraits (`PartialOrd`, `Eq`, and `PartialEq`) must also be consistent. The previous implementations would not "notice" any problem, but the new implementations have a good chance of detecting inconsistencies, throwing a panic rather than returning knowingly unsorted data. * [In very rare cases, a change in the internal evaluation order of the trait solver may result in new fatal overflow errors.] (rust-lang/rust#126128) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Add a Rust-for Linux `auto` CI job to check kernel builds.] (rust-lang/rust#125209)
Summary: Rust 1.81 introduced new [lifetime rules](rust-lang/rust#117967), which opaque-ke, a crate we depend on, violated. The maintainers of that crate have introduced a new version that satisifies these new rules, and we have upgraded to this version in D13895. Now that we've upgraded the dependency, we should bump Rust to the latest stable version. Depends on D13895 Test Plan: All crates build locally and in Docker (CI) Reviewers: will, bartek Subscribers:
Summary: Rust 1.81 introduced new [lifetime rules](rust-lang/rust#117967), which opaque-ke, a crate we depend on, violated. The maintainers of that crate have introduced a new version that satisifies these new rules, and we have upgraded to this version in D13895. Now that we've upgraded the dependency, we should bump Rust to the latest stable version. Depends on D13895 Test Plan: All crates build locally and in Docker (CI) Reviewers: will, bartek Subscribers: ashoat, tomek Differential Revision: https://phab.comm.dev/D13896
Summary: Rust 1.81 introduced new [lifetime rules](rust-lang/rust#117967), which opaque-ke, a crate we depend on, violated. The maintainers of that crate have introduced a new version that satisifies these new rules, and we have upgraded to this version in D13895. Now that we've upgraded the dependency, we should bump Rust to the latest stable version. EDIT: we can't upgrade to 1.82, the latest stable version, because of an issue with `wasm-bindgen`: https://linear.app/comm/issue/ENG-9892/cant-upgrade-to-rust-182 Depends on D13895 Test Plan: All crates build locally and in Docker (CI) Reviewers: will, bartek Subscribers: ashoat, tomek Differential Revision: https://phab.comm.dev/D13896
Summary: Rust 1.81 introduced new [lifetime rules](rust-lang/rust#117967), which opaque-ke, a crate we depend on, violated. The maintainers of that crate have introduced a new version that satisifies these new rules, and we have upgraded to this version in D13895. Now that we've upgraded the dependency, we should bump Rust to the latest stable version. EDIT: we can't upgrade to 1.82, the latest stable version, because of an issue with `wasm-bindgen`: https://linear.app/comm/issue/ENG-9892/cant-upgrade-to-rust-182 Depends on D13895 Test Plan: All crates build locally and in Docker (CI) Reviewers: will, bartek Subscribers: ashoat, tomek Differential Revision: https://phab.comm.dev/D13896
Summary: Rust 1.81 introduced new [lifetime rules](rust-lang/rust#117967), which opaque-ke, a crate we depend on, violated. The maintainers of that crate have introduced a new version that satisifies these new rules, and we have upgraded to this version in D13895. Now that we've upgraded the dependency, we should bump Rust to the latest stable version. EDIT: we can't upgrade to 1.82, the latest stable version, because of an issue with `wasm-bindgen`: https://linear.app/comm/issue/ENG-9892/cant-upgrade-to-rust-182 Depends on D13895 Test Plan: All crates build locally and in Docker (CI) Reviewers: will, bartek Reviewed By: will, bartek Subscribers: ashoat, tomek Differential Revision: https://phab.comm.dev/D13896
Pkgsrc changes: * Adapt patches, apply to new vendored crates where needed. * Back-port rust pull request 130110, "make dist vendoring configurable" * Disable "dist vendoring", otherwise cargo would try to access the network during the build phase. Upstream changes: Version 1.81.0 (2024-09-05) ========================== Language -------- - [Abort on uncaught panics in `extern "C"` functions.] (rust-lang/rust#116088) - [Fix ambiguous cases of multiple `&` in elided self lifetimes.] (rust-lang/rust#117967) - [Stabilize `#[expect]` for lints (RFC 2383),] (rust-lang/rust#120924) like `#[allow]` with a warning if the lint is _not_ fulfilled. - [Change method resolution to constrain hidden types instead of rejecting method candidates.] (rust-lang/rust#123962) - [Bump `elided_lifetimes_in_associated_constant` to deny.] (rust-lang/rust#124211) - [`offset_from`: always allow pointers to point to the same address.] (rust-lang/rust#124921) - [Allow constraining opaque types during subtyping in the trait system.] (rust-lang/rust#125447) - [Allow constraining opaque types during various unsizing casts.] (rust-lang/rust#125610) - [Deny keyword lifetimes pre-expansion.] (rust-lang/rust#126762) Compiler -------- - [Make casts of pointers to trait objects stricter.] (rust-lang/rust#120248) - [Check alias args for well-formedness even if they have escaping bound vars.] (rust-lang/rust#123737) - [Deprecate no-op codegen option `-Cinline-threshold=...`.] (rust-lang/rust#124712) - [Re-implement a type-size based limit.] (rust-lang/rust#125507) - [Properly account for alignment in `transmute` size checks.] (rust-lang/rust#125740) - [Remove the `box_pointers` lint.] (rust-lang/rust#126018) - [Ensure the interpreter checks bool/char for validity when they are used in a cast.] (rust-lang/rust#126265) - [Improve coverage instrumentation for functions containing nested items.] (rust-lang/rust#127199) - Target changes: - [Add Tier 3 `no_std` Xtensa targets:] (rust-lang/rust#125141) `xtensa-esp32-none-elf`, `xtensa-esp32s2-none-elf`, `xtensa-esp32s3-none-elf` - [Add Tier 3 `std` Xtensa targets:] (rust-lang/rust#126380) `xtensa-esp32-espidf`, `xtensa-esp32s2-espidf`, `xtensa-esp32s3-espidf` - [Add Tier 3 i686 Redox OS target:] (rust-lang/rust#126192) `i686-unknown-redox` - [Promote `arm64ec-pc-windows-msvc` to Tier 2.] (rust-lang/rust#126039) - [Promote `wasm32-wasip2` to Tier 2.] (rust-lang/rust#126967) - [Promote `loongarch64-unknown-linux-musl` to Tier 2 with host tools.] (rust-lang/rust#126298) - [Enable full tools and profiler for LoongArch Linux targets.] (rust-lang/rust#127078) - [Unconditionally warn on usage of `wasm32-wasi`.] (rust-lang/rust#126662) (see compatibility note below) - Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Split core's `PanicInfo` and std's `PanicInfo`.] (rust-lang/rust#115974) (see compatibility note below) - [Generalize `{Rc,Arc}::make_mut()` to unsized types.] (rust-lang/rust#116113) - [Replace sort implementations with stable `driftsort` and unstable `ipnsort`.] (rust-lang/rust#124032) All `slice::sort*` and `slice::select_nth*` methods are expected to see significant performance improvements. See the [research project] (https://github.com/Voultapher/sort-research-rs) for more details. - [Document behavior of `create_dir_all` with respect to empty paths.] (rust-lang/rust#125112) - [Fix interleaved output in the default panic hook when multiple threads panic simultaneously.] (rust-lang/rust#127397) - Fix `Command`'s batch files argument escaping not working when file name has trailing whitespace or periods (CVE-2024-43402). Stabilized APIs --------------- - [`core::error`] (https://doc.rust-lang.org/stable/core/error/index.html) - [`hint::assert_unchecked`] (https://doc.rust-lang.org/stable/core/hint/fn.assert_unchecked.html) - [`fs::exists`] (https://doc.rust-lang.org/stable/std/fs/fn.exists.html) - [`AtomicBool::fetch_not`] (https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicBool.html#method.fetch_not) - [`Duration::abs_diff`] (https://doc.rust-lang.org/stable/core/time/struct.Duration.html#method.abs_diff) - [`IoSlice::advance`] (https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance) - [`IoSlice::advance_slices`] (https://doc.rust-lang.org/stable/std/io/struct.IoSlice.html#method.advance_slices) - [`IoSliceMut::advance`] (https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance) - [`IoSliceMut::advance_slices`] (https://doc.rust-lang.org/stable/std/io/struct.IoSliceMut.html#method.advance_slices) - [`PanicHookInfo`] (https://doc.rust-lang.org/stable/std/panic/struct.PanicHookInfo.html) - [`PanicInfo::message`] (https://doc.rust-lang.org/stable/core/panic/struct.PanicInfo.html#method.message) - [`PanicMessage`] (https://doc.rust-lang.org/stable/core/panic/struct.PanicMessage.html) These APIs are now stable in const contexts: - [`char::from_u32_unchecked`] (https://doc.rust-lang.org/stable/core/char/fn.from_u32_unchecked.html) (function) - [`char::from_u32_unchecked`] (https://doc.rust-lang.org/stable/core/primitive.char.html#method.from_u32_unchecked) (method) - [`CStr::count_bytes`] (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes) - [`CStr::from_ptr`] (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.from_ptr) Cargo ----- - [Generated `.cargo_vcs_info.json` is always included, even when `--allow-dirty` is passed.] (rust-lang/cargo#13960) - [Disallow `package.license-file` and `package.readme` pointing to non-existent files during packaging.] (rust-lang/cargo#13921) - [Disallow passing `--release`/`--debug` flag along with the `--profile` flag.] (rust-lang/cargo#13971) - [Remove `lib.plugin` key support in `Cargo.toml`. Rust plugin support has been deprecated for four years and was removed in 1.75.0.] (rust-lang/cargo#13902) Compatibility Notes ------------------- * Usage of the `wasm32-wasi` target will now issue a compiler warning and request users switch to the `wasm32-wasip1` target instead. Both targets are the same, `wasm32-wasi` is only being renamed, and this [change to the WASI target] (https://blog.rust-lang.org/2024/04/09/updates-to-rusts-wasi-targets.html) is being done to enable removing `wasm32-wasi` in January 2025. * We have renamed `std::panic::PanicInfo` to `std::panic::PanicHookInfo`. The old name will continue to work as an alias, but will result in a deprecation warning starting in Rust 1.82.0. `core::panic::PanicInfo` will remain unchanged, however, as this is now a *different type*. The reason is that these types have different roles: `std::panic::PanicHookInfo` is the argument to the [panic hook](https://doc.rust-lang.org/stable/std/panic/fn.set_hook.html) in std context (where panics can have an arbitrary payload), while `core::panic::PanicInfo` is the argument to the [`#[panic_handler]`](https://doc.rust-lang.org/nomicon/panic-handler.html) in no_std context (where panics always carry a formatted *message*). Separating these types allows us to add more useful methods to these types, such as `std::panic::PanicHookInfo::payload_as_str()` and `core::panic::PanicInfo::message()`. * The new sort implementations may panic if a type's implementation of [`Ord`](https://doc.rust-lang.org/std/cmp/trait.Ord.html) (or the given comparison function) does not implement a [total order](https://en.wikipedia.org/wiki/Total_order) as the trait requires. `Ord`'s supertraits (`PartialOrd`, `Eq`, and `PartialEq`) must also be consistent. The previous implementations would not "notice" any problem, but the new implementations have a good chance of detecting inconsistencies, throwing a panic rather than returning knowingly unsorted data. * [In very rare cases, a change in the internal evaluation order of the trait solver may result in new fatal overflow errors.] (rust-lang/rust#126128) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Add a Rust-for Linux `auto` CI job to check kernel builds.] (rust-lang/rust#125209)
This change proposes simpler rules to identify the lifetime on
self
parameters which may be used to elide a return type lifetime.The old rules
(copied from this comment)
Most of the code can be found in late.rs and acts on AST types. The function resolve_fn_params, in the success case, returns a single lifetime which can be used to elide the lifetime of return types.
Here's how:
self
search rules", below(In practice the code does extra work to assemble good diagnostic information, so it's not quite laid out like the above.)
self
search rulesThis is primarily handled in find_lifetime_for_self , and is described slightly here already. The code:
self
parameter (there's some complexity about resolving various special cases, but it's essentially just walking the type as far as I can see)Self
(either spelledSelf
or by some alias resolution which I don't fully understand), then we'll add that to a set of candidate lifetimesRegular parameter search rules
self
lifetime parameter already, we'll return this lifetime.The new rules
There are no changes to the "regular parameter search rules" or to the overall flow, only to the
self
search rules which are now:self
parameter, searching for lifetimes of reference types whose referent containsSelf
.1Examples that were accepted before and will now be rejected
Examples that change the elided lifetime
Examples that were rejected before and will now be accepted
edit: old PR description:
resulted in a confusing error.
resulted in no error or warning, despite apparent ambiguity over the elided lifetime.
Fixes #117715
Footnotes
this prevents us from considering lifetimes from inside of the self-type ↩