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Rust 2015: No longer downgrade NLL errors #64221
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Marking as blocked on changing nightly to 1.40. |
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r=me with the couple of nits addressed
cc @rust-lang/lang
//~| WARNING cannot return reference to temporary value | ||
//~| WARNING this error has been downgraded to a warning | ||
//~| WARNING this warning will become a hard error in the future | ||
//~| ERROR cannot return reference to temporary value |
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Note to self: min const fn qualification failing causing temporary promotion to fail really should be fixed.
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Might be worth filing an issue; cc @oli-obk @ecstatic-morse @eddyb
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Should probably go away once we decouple promotion and const-checking.
// mode and changes some error messages. | ||
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||
// FIXME(Centril): This test is probably obsolete now and `nll` should become | ||
// `accepted`. |
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Probably, the -Z
flags are probably sufficient for the remaining borrowck configuration. This can be a future PR.
src/test/ui/issues/issue-45696-scribble-on-boxed-borrow.migrate.stderr
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Fixed the two currently actionable nits (+ rebased -- don't want to rebuild LLVM :P). @bors r=matthewjasper 🚀 |
📌 Commit 4503ad4 has been approved by |
…hewjasper Rust 2015: No longer downgrade NLL errors As per decision on a language team meeting as described in rust-lang#63565 (comment), in Rust 2015, we refuse to downgrade NLL errors, that AST borrowck accepts, into warnings and keep them as hard errors. The remaining work to throw out AST borrowck and adjust some tests still remains after this PR. Fixes rust-lang#38899 Fixes rust-lang#53432 Fixes rust-lang#45157 Fixes rust-lang#31567 Fixes rust-lang#27868 Fixes rust-lang#47366 r? @matthewjasper
…hewjasper Rust 2015: No longer downgrade NLL errors As per decision on a language team meeting as described in rust-lang#63565 (comment), in Rust 2015, we refuse to downgrade NLL errors, that AST borrowck accepts, into warnings and keep them as hard errors. The remaining work to throw out AST borrowck and adjust some tests still remains after this PR. Fixes rust-lang#38899 Fixes rust-lang#53432 Fixes rust-lang#45157 Fixes rust-lang#31567 Fixes rust-lang#27868 Fixes rust-lang#47366 r? @matthewjasper
📌 Commit 9a2cc54 has been approved by |
…hewjasper Rust 2015: No longer downgrade NLL errors As per decision on a language team meeting as described in rust-lang#63565 (comment), in Rust 2015, we refuse to downgrade NLL errors, that AST borrowck accepts, into warnings and keep them as hard errors. The remaining work to throw out AST borrowck and adjust some tests still remains after this PR. Fixes rust-lang#38899 Fixes rust-lang#53432 Fixes rust-lang#45157 Fixes rust-lang#31567 Fixes rust-lang#27868 Fixes rust-lang#47366 r? @matthewjasper
@bors r=matthewjasper Carried over @pnkfelix's note in #64790 (comment) to this PR. |
📌 Commit 5a0e461 has been approved by |
…hewjasper Rust 2015: No longer downgrade NLL errors As per decision on a language team meeting as described in rust-lang#63565 (comment), in Rust 2015, we refuse to downgrade NLL errors, that AST borrowck accepts, into warnings and keep them as hard errors. The remaining work to throw out AST borrowck and adjust some tests still remains after this PR. Fixes rust-lang#38899 Fixes rust-lang#53432 Fixes rust-lang#45157 Fixes rust-lang#31567 Fixes rust-lang#27868 Fixes rust-lang#47366 r? @matthewjasper
Rest In Peace, AST borrowck (2012-2019) After having served us for 7 years, the AST borrow-checker is no more. This PR starts from the commit `rm -rf librustc_ast_borrowck`, building on #64221, and is probably best read commit by commit. Migrate mode is not removed yet as it may be useful for NLL => polonius and it is also used for the `mutable_borrow_reservation_conflict` issue (#59159). r? @matthewjasper ------------------------ ![ast-borrowck-rip](https://user-images.githubusercontent.com/855702/65646791-91a87600-dffc-11e9-9814-deed6b821c80.png)
Version 1.40.0 (2019-12-19) =========================== Language -------- - [You can now use tuple `struct`s and tuple `enum` variant's constructors in `const` contexts.][65188] e.g. ```rust pub struct Point(i32, i32); const ORIGIN: Point = { let constructor = Point; constructor(0, 0) }; ``` - [You can now mark `struct`s, `enum`s, and `enum` variants with the `#[non_exhaustive]` attribute to indicate that there may be variants or fields added in the future.][64639] For example this requires adding a wild-card branch (`_ => {}`) to any match statements on a non-exhaustive `enum`. [(RFC 2008)] - [You can now use function-like procedural macros in `extern` blocks and in type positions.][63931] e.g. `type Generated = macro!();` - [Function-like and attribute procedural macros can now emit `macro_rules!` items, so you can now have your macros generate macros.][64035] - [The `meta` pattern matcher in `macro_rules!` now correctly matches the modern attribute syntax.][63674] For example `(#[$m:meta])` now matches `#[attr]`, `#[attr{tokens}]`, `#[attr[tokens]]`, and `#[attr(tokens)]`. Compiler -------- - [Added tier 3 support\* for the `thumbv7neon-unknown-linux-musleabihf` target.][66103] - [Added tier 3 support for the `aarch64-unknown-none-softfloat` target.][64589] - [Added tier 3 support for the `mips64-unknown-linux-muslabi64`, and `mips64el-unknown-linux-muslabi64` targets.][65843] \* Refer to Rust's [platform support page][forge-platform-support] for more information on Rust's tiered platform support. Libraries --------- - [The `is_power_of_two` method on unsigned numeric types is now a `const` function.][65092] Stabilized APIs --------------- - [`BTreeMap::get_key_value`] - [`HashMap::get_key_value`] - [`Option::as_deref_mut`] - [`Option::as_deref`] - [`Option::flatten`] - [`UdpSocket::peer_addr`] - [`f32::to_be_bytes`] - [`f32::to_le_bytes`] - [`f32::to_ne_bytes`] - [`f64::to_be_bytes`] - [`f64::to_le_bytes`] - [`f64::to_ne_bytes`] - [`f32::from_be_bytes`] - [`f32::from_le_bytes`] - [`f32::from_ne_bytes`] - [`f64::from_be_bytes`] - [`f64::from_le_bytes`] - [`f64::from_ne_bytes`] - [`mem::take`] - [`slice::repeat`] - [`todo!`] Cargo ----- - [Cargo will now always display warnings, rather than only on fresh builds.][cargo/7450] - [Feature flags (except `--all-features`) passed to a virtual workspace will now produce an error.][cargo/7507] Previously these flags were ignored. - [You can now publish `dev-dependencies` without including a `version`.][cargo/7333] Misc ---- - [You can now specify the `#[cfg(doctest)]` attribute to include an item only when running documentation tests with `rustdoc`.][63803] Compatibility Notes ------------------- - [As previously announced, any previous NLL warnings in the 2015 edition are now hard errors.][64221] - [The `include!` macro will now warn if it failed to include the entire file.][64284] The `include!` macro unintentionally only includes the first _expression_ in a file, and this can be unintuitive. This will become either a hard error in a future release, or the behavior may be fixed to include all expressions as expected. - [Using `#[inline]` on function prototypes and consts now emits a warning under `unused_attribute` lint.][65294] Using `#[inline]` anywhere else inside traits or `extern` blocks now correctly emits a hard error. [65294]: rust-lang/rust#65294 [66103]: rust-lang/rust#66103 [65843]: rust-lang/rust#65843 [65188]: rust-lang/rust#65188 [65092]: rust-lang/rust#65092 [64589]: rust-lang/rust#64589 [64639]: rust-lang/rust#64639 [64221]: rust-lang/rust#64221 [64284]: rust-lang/rust#64284 [63931]: rust-lang/rust#63931 [64035]: rust-lang/rust#64035 [63674]: rust-lang/rust#63674 [63803]: rust-lang/rust#63803 [cargo/7450]: rust-lang/cargo#7450 [cargo/7507]: rust-lang/cargo#7507 [cargo/7525]: rust-lang/cargo#7525 [cargo/7333]: rust-lang/cargo#7333 [(rfc 2008)]: https://rust-lang.github.io/rfcs/2008-non-exhaustive.html [`f32::to_be_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_be_bytes [`f32::to_le_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_le_bytes [`f32::to_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_ne_bytes [`f64::to_be_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_be_bytes [`f64::to_le_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_le_bytes [`f64::to_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_ne_bytes [`f32::from_be_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_be_bytes [`f32::from_le_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_le_bytes [`f32::from_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_ne_bytes [`f64::from_be_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_be_bytes [`f64::from_le_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_le_bytes [`f64::from_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_ne_bytes [`option::flatten`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.flatten [`option::as_deref`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.as_deref [`option::as_deref_mut`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.as_deref_mut [`hashmap::get_key_value`]: https://doc.rust-lang.org/std/collections/struct.HashMap.html#method.get_key_value [`btreemap::get_key_value`]: https://doc.rust-lang.org/std/collections/struct.BTreeMap.html#method.get_key_value [`slice::repeat`]: https://doc.rust-lang.org/std/primitive.slice.html#method.repeat [`mem::take`]: https://doc.rust-lang.org/std/mem/fn.take.html [`udpsocket::peer_addr`]: https://doc.rust-lang.org/std/net/struct.UdpSocket.html#method.peer_addr [`todo!`]: https://doc.rust-lang.org/std/macro.todo.html
Version 1.40.0 (2019-12-19) =========================== Language -------- - [You can now use tuple `struct`s and tuple `enum` variant's constructors in `const` contexts.][65188] e.g. ```rust pub struct Point(i32, i32); const ORIGIN: Point = { let constructor = Point; constructor(0, 0) }; ``` - [You can now mark `struct`s, `enum`s, and `enum` variants with the `#[non_exhaustive]` attribute to indicate that there may be variants or fields added in the future.][64639] For example this requires adding a wild-card branch (`_ => {}`) to any match statements on a non-exhaustive `enum`. [(RFC 2008)] - [You can now use function-like procedural macros in `extern` blocks and in type positions.][63931] e.g. `type Generated = macro!();` - [Function-like and attribute procedural macros can now emit `macro_rules!` items, so you can now have your macros generate macros.][64035] - [The `meta` pattern matcher in `macro_rules!` now correctly matches the modern attribute syntax.][63674] For example `(#[$m:meta])` now matches `#[attr]`, `#[attr{tokens}]`, `#[attr[tokens]]`, and `#[attr(tokens)]`. Compiler -------- - [Added tier 3 support\* for the `thumbv7neon-unknown-linux-musleabihf` target.][66103] - [Added tier 3 support for the `aarch64-unknown-none-softfloat` target.][64589] - [Added tier 3 support for the `mips64-unknown-linux-muslabi64`, and `mips64el-unknown-linux-muslabi64` targets.][65843] \* Refer to Rust's [platform support page][forge-platform-support] for more information on Rust's tiered platform support. Libraries --------- - [The `is_power_of_two` method on unsigned numeric types is now a `const` function.][65092] Stabilized APIs --------------- - [`BTreeMap::get_key_value`] - [`HashMap::get_key_value`] - [`Option::as_deref_mut`] - [`Option::as_deref`] - [`Option::flatten`] - [`UdpSocket::peer_addr`] - [`f32::to_be_bytes`] - [`f32::to_le_bytes`] - [`f32::to_ne_bytes`] - [`f64::to_be_bytes`] - [`f64::to_le_bytes`] - [`f64::to_ne_bytes`] - [`f32::from_be_bytes`] - [`f32::from_le_bytes`] - [`f32::from_ne_bytes`] - [`f64::from_be_bytes`] - [`f64::from_le_bytes`] - [`f64::from_ne_bytes`] - [`mem::take`] - [`slice::repeat`] - [`todo!`] Cargo ----- - [Cargo will now always display warnings, rather than only on fresh builds.][cargo/7450] - [Feature flags (except `--all-features`) passed to a virtual workspace will now produce an error.][cargo/7507] Previously these flags were ignored. - [You can now publish `dev-dependencies` without including a `version`.][cargo/7333] Misc ---- - [You can now specify the `#[cfg(doctest)]` attribute to include an item only when running documentation tests with `rustdoc`.][63803] Compatibility Notes ------------------- - [As previously announced, any previous NLL warnings in the 2015 edition are now hard errors.][64221] - [The `include!` macro will now warn if it failed to include the entire file.][64284] The `include!` macro unintentionally only includes the first _expression_ in a file, and this can be unintuitive. This will become either a hard error in a future release, or the behavior may be fixed to include all expressions as expected. - [Using `#[inline]` on function prototypes and consts now emits a warning under `unused_attribute` lint.][65294] Using `#[inline]` anywhere else inside traits or `extern` blocks now correctly emits a hard error. [65294]: rust-lang/rust#65294 [66103]: rust-lang/rust#66103 [65843]: rust-lang/rust#65843 [65188]: rust-lang/rust#65188 [65092]: rust-lang/rust#65092 [64589]: rust-lang/rust#64589 [64639]: rust-lang/rust#64639 [64221]: rust-lang/rust#64221 [64284]: rust-lang/rust#64284 [63931]: rust-lang/rust#63931 [64035]: rust-lang/rust#64035 [63674]: rust-lang/rust#63674 [63803]: rust-lang/rust#63803 [cargo/7450]: rust-lang/cargo#7450 [cargo/7507]: rust-lang/cargo#7507 [cargo/7525]: rust-lang/cargo#7525 [cargo/7333]: rust-lang/cargo#7333 [(rfc 2008)]: https://rust-lang.github.io/rfcs/2008-non-exhaustive.html [`f32::to_be_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_be_bytes [`f32::to_le_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_le_bytes [`f32::to_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_ne_bytes [`f64::to_be_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_be_bytes [`f64::to_le_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_le_bytes [`f64::to_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_ne_bytes [`f32::from_be_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_be_bytes [`f32::from_le_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_le_bytes [`f32::from_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_ne_bytes [`f64::from_be_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_be_bytes [`f64::from_le_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_le_bytes [`f64::from_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_ne_bytes [`option::flatten`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.flatten [`option::as_deref`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.as_deref [`option::as_deref_mut`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.as_deref_mut [`hashmap::get_key_value`]: https://doc.rust-lang.org/std/collections/struct.HashMap.html#method.get_key_value [`btreemap::get_key_value`]: https://doc.rust-lang.org/std/collections/struct.BTreeMap.html#method.get_key_value [`slice::repeat`]: https://doc.rust-lang.org/std/primitive.slice.html#method.repeat [`mem::take`]: https://doc.rust-lang.org/std/mem/fn.take.html [`udpsocket::peer_addr`]: https://doc.rust-lang.org/std/net/struct.UdpSocket.html#method.peer_addr [`todo!`]: https://doc.rust-lang.org/std/macro.todo.html
I've been trying to keep the crate compatible with Rust 2018, which corresponds to Rust version 1.31.0. However, this has proven impossible because of how our dependencies keep releasing new patch versions that push up the minimum required Rust version. Because of this, the current code no longer compiles with Rust 1.31.0 because `cargo sync` will pull in too new versions of the direct and transitive dependencies. This happens even if there are no changes in `version-sync`. The failure to compile shows up as spurious and unexpected build failures in our CI, which in turn makes it hard to trust CI. I'm concluding that it's infeasible to keep `version-sync` compatible with any particular version of Rust. While not perfect, we'll track the latest stable version of Rust from now on. This is not perfect since even stable Rust sometimes decides to turn warnings into hard errors: rust-lang/rust#64221
I've been trying to keep the crate compatible with Rust 2018, which corresponds to Rust version 1.31.0. However, this has proven impossible because of how our dependencies keep releasing new patch versions that push up the minimum required Rust version. Because of this, the current code no longer compiles with Rust 1.31.0 because `cargo sync` will pull in too new versions of the direct and transitive dependencies. This happens even if there are no changes in `version-sync`. The failure to compile shows up as spurious and unexpected build failures in our CI, which in turn makes it hard to trust CI. I'm concluding that it's infeasible to keep `version-sync` compatible with any particular version of Rust. While not perfect, we'll track the latest stable version of Rust from now on. This is not perfect since even stable Rust sometimes decides to turn warnings into hard errors: rust-lang/rust#64221
I've been trying to keep the crate compatible with Rust 2018, which corresponds to Rust version 1.31.0. However, this has proven impossible because of how our dependencies keep releasing new patch versions that push up the minimum required Rust version. Because of this, the current code no longer compiles with Rust 1.31.0 because `cargo sync` will pull in too new versions of the direct and transitive dependencies. This happens even if there are no changes in `version-sync`. The failure to compile shows up as spurious and unexpected build failures in our CI, which in turn makes it hard to trust CI. I'm concluding that it's infeasible to keep `version-sync` compatible with any particular version of Rust. While not perfect, we'll track the latest stable version of Rust from now on. This is not perfect since even stable Rust sometimes decides to turn warnings into hard errors: rust-lang/rust#64221
I've been trying to keep the crate compatible with Rust 2018, which corresponds to Rust version 1.31.0. However, this has proven impossible because of how our dependencies keep releasing new patch versions that push up the minimum required Rust version. Because of this, the current code no longer compiles with Rust 1.31.0 because `cargo sync` will pull in too new versions of the direct and transitive dependencies. This happens even if there are no changes in `version-sync`. The failure to compile shows up as spurious and unexpected build failures in our CI, which in turn makes it hard to trust CI. I'm concluding that it's infeasible to keep `version-sync` compatible with any particular version of Rust. While not perfect, we'll track the latest stable version of Rust from now on. This is not perfect since even stable Rust sometimes decides to turn warnings into hard errors: rust-lang/rust#64221
…matsakis Remove migrate borrowck mode Closes rust-lang#58781 Closes rust-lang#43234 # Stabilization proposal This PR proposes the stabilization of `#![feature(nll)]` and the removal of `-Z borrowck`. Current borrow checking behavior of item bodies is currently done by first infering regions *lexically* and reporting any errors during HIR type checking. If there *are* any errors, then MIR borrowck (NLL) never occurs. If there *aren't* any errors, then MIR borrowck happens and any errors there would be reported. This PR removes the lexical region check of item bodies entirely and only uses MIR borrowck. Because MIR borrowck could never *not* be run for a compiled program, this should not break any programs. It does, however, change diagnostics significantly and allows a slightly larger set of programs to compile. Tracking issue: rust-lang#43234 RFC: https://github.com/rust-lang/rfcs/blob/master/text/2094-nll.md Version: 1.63 (2022-06-30 => beta, 2022-08-11 => stable). ## Motivation Over time, the Rust borrow checker has become "smarter" and thus allowed more programs to compile. There have been three different implementations: AST borrowck, MIR borrowck, and polonius (well, in progress). Additionally, there is the "lexical region resolver", which (roughly) solves the constraints generated through HIR typeck. It is not a full borrow checker, but does emit some errors. The AST borrowck was the original implementation of the borrow checker and was part of the initially stabilized Rust 1.0. In mid 2017, work began to implement the current MIR borrow checker and that effort ompleted by the end of 2017, for the most part. During 2018, efforts were made to migrate away from the AST borrow checker to the MIR borrow checker - eventually culminating into "migrate" mode - where HIR typeck with lexical region resolving following by MIR borrow checking - being active by default in the 2018 edition. In early 2019, migrate mode was turned on by default in the 2015 edition as well, but with MIR borrowck errors emitted as warnings. By late 2019, these warnings were upgraded to full errors. This was followed by the complete removal of the AST borrow checker. In the period since, various errors emitted by the MIR borrow checker have been improved to the point that they are mostly the same or better than those emitted by the lexical region resolver. While there do remain some degradations in errors (tracked under the [NLL-diagnostics tag](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-diagnostics), those are sufficiently small and rare enough that increased flexibility of MIR borrow check-only is now a worthwhile tradeoff. ## What is stabilized As said previously, this does not fundamentally change the landscape of accepted programs. However, there are a [few](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-fixed-by-NLL) cases where programs can compile under `feature(nll)`, but not otherwise. There are two notable patterns that are "fixed" by this stabilization. First, the `scoped_threads` feature, which is a continutation of a pre-1.0 API, can sometimes emit a [weird lifetime error](rust-lang#95527) without NLL. Second, actually seen in the standard library. In the `Extend` impl for `HashMap`, there is an implied bound of `K: 'a` that is available with NLL on but not without - this is utilized in the impl. As mentioned before, there are a large number of diagnostic differences. Most of them are better, but some are worse. None are serious or happen often enough to need to block this PR. The biggest change is the loss of error code for a number of lifetime errors in favor of more general "lifetime may not live long enough" error. While this may *seem* bad, the former error codes were just attempts to somewhat-arbitrarily bin together lifetime errors of the same type; however, on paper, they end up being roughly the same with roughly the same kinds of solutions. ## What isn't stabilized This PR does not completely remove the lexical region resolver. In the future, it may be possible to remove that (while still keeping HIR typeck) or to remove it together with HIR typeck. ## Tests Many test outputs get updated by this PR. However, there are number of tests specifically geared towards NLL under `src/test/ui/nll` ## History * On 2017-07-14, [tracking issue opened](rust-lang#43234) * On 2017-07-20, [initial empty MIR pass added](rust-lang#43271) * On 2017-08-29, [RFC opened](rust-lang/rfcs#2094) * On 2017-11-16, [Integrate MIR type-checker with NLL](rust-lang#45825) * On 2017-12-20, [NLL feature complete](rust-lang#46862) * On 2018-07-07, [Don't run AST borrowck on mir mode](rust-lang#52083) * On 2018-07-27, [Add migrate mode](rust-lang#52681) * On 2019-04-22, [Enable migrate mode on 2015 edition](rust-lang#59114) * On 2019-08-26, [Don't downgrade errors on 2015 edition](rust-lang#64221) * On 2019-08-27, [Remove AST borrowck](rust-lang#64790)
Remove migrate borrowck mode Closes #58781 Closes #43234 # Stabilization proposal This PR proposes the stabilization of `#![feature(nll)]` and the removal of `-Z borrowck`. Current borrow checking behavior of item bodies is currently done by first infering regions *lexically* and reporting any errors during HIR type checking. If there *are* any errors, then MIR borrowck (NLL) never occurs. If there *aren't* any errors, then MIR borrowck happens and any errors there would be reported. This PR removes the lexical region check of item bodies entirely and only uses MIR borrowck. Because MIR borrowck could never *not* be run for a compiled program, this should not break any programs. It does, however, change diagnostics significantly and allows a slightly larger set of programs to compile. Tracking issue: #43234 RFC: https://github.com/rust-lang/rfcs/blob/master/text/2094-nll.md Version: 1.63 (2022-06-30 => beta, 2022-08-11 => stable). ## Motivation Over time, the Rust borrow checker has become "smarter" and thus allowed more programs to compile. There have been three different implementations: AST borrowck, MIR borrowck, and polonius (well, in progress). Additionally, there is the "lexical region resolver", which (roughly) solves the constraints generated through HIR typeck. It is not a full borrow checker, but does emit some errors. The AST borrowck was the original implementation of the borrow checker and was part of the initially stabilized Rust 1.0. In mid 2017, work began to implement the current MIR borrow checker and that effort ompleted by the end of 2017, for the most part. During 2018, efforts were made to migrate away from the AST borrow checker to the MIR borrow checker - eventually culminating into "migrate" mode - where HIR typeck with lexical region resolving following by MIR borrow checking - being active by default in the 2018 edition. In early 2019, migrate mode was turned on by default in the 2015 edition as well, but with MIR borrowck errors emitted as warnings. By late 2019, these warnings were upgraded to full errors. This was followed by the complete removal of the AST borrow checker. In the period since, various errors emitted by the MIR borrow checker have been improved to the point that they are mostly the same or better than those emitted by the lexical region resolver. While there do remain some degradations in errors (tracked under the [NLL-diagnostics tag](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-diagnostics), those are sufficiently small and rare enough that increased flexibility of MIR borrow check-only is now a worthwhile tradeoff. ## What is stabilized As said previously, this does not fundamentally change the landscape of accepted programs. However, there are a [few](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-fixed-by-NLL) cases where programs can compile under `feature(nll)`, but not otherwise. There are two notable patterns that are "fixed" by this stabilization. First, the `scoped_threads` feature, which is a continutation of a pre-1.0 API, can sometimes emit a [weird lifetime error](rust-lang/rust#95527) without NLL. Second, actually seen in the standard library. In the `Extend` impl for `HashMap`, there is an implied bound of `K: 'a` that is available with NLL on but not without - this is utilized in the impl. As mentioned before, there are a large number of diagnostic differences. Most of them are better, but some are worse. None are serious or happen often enough to need to block this PR. The biggest change is the loss of error code for a number of lifetime errors in favor of more general "lifetime may not live long enough" error. While this may *seem* bad, the former error codes were just attempts to somewhat-arbitrarily bin together lifetime errors of the same type; however, on paper, they end up being roughly the same with roughly the same kinds of solutions. ## What isn't stabilized This PR does not completely remove the lexical region resolver. In the future, it may be possible to remove that (while still keeping HIR typeck) or to remove it together with HIR typeck. ## Tests Many test outputs get updated by this PR. However, there are number of tests specifically geared towards NLL under `src/test/ui/nll` ## History * On 2017-07-14, [tracking issue opened](rust-lang/rust#43234) * On 2017-07-20, [initial empty MIR pass added](rust-lang/rust#43271) * On 2017-08-29, [RFC opened](rust-lang/rfcs#2094) * On 2017-11-16, [Integrate MIR type-checker with NLL](rust-lang/rust#45825) * On 2017-12-20, [NLL feature complete](rust-lang/rust#46862) * On 2018-07-07, [Don't run AST borrowck on mir mode](rust-lang/rust#52083) * On 2018-07-27, [Add migrate mode](rust-lang/rust#52681) * On 2019-04-22, [Enable migrate mode on 2015 edition](rust-lang/rust#59114) * On 2019-08-26, [Don't downgrade errors on 2015 edition](rust-lang/rust#64221) * On 2019-08-27, [Remove AST borrowck](rust-lang/rust#64790)
Remove migrate borrowck mode Closes #58781 Closes #43234 # Stabilization proposal This PR proposes the stabilization of `#![feature(nll)]` and the removal of `-Z borrowck`. Current borrow checking behavior of item bodies is currently done by first infering regions *lexically* and reporting any errors during HIR type checking. If there *are* any errors, then MIR borrowck (NLL) never occurs. If there *aren't* any errors, then MIR borrowck happens and any errors there would be reported. This PR removes the lexical region check of item bodies entirely and only uses MIR borrowck. Because MIR borrowck could never *not* be run for a compiled program, this should not break any programs. It does, however, change diagnostics significantly and allows a slightly larger set of programs to compile. Tracking issue: #43234 RFC: https://github.com/rust-lang/rfcs/blob/master/text/2094-nll.md Version: 1.63 (2022-06-30 => beta, 2022-08-11 => stable). ## Motivation Over time, the Rust borrow checker has become "smarter" and thus allowed more programs to compile. There have been three different implementations: AST borrowck, MIR borrowck, and polonius (well, in progress). Additionally, there is the "lexical region resolver", which (roughly) solves the constraints generated through HIR typeck. It is not a full borrow checker, but does emit some errors. The AST borrowck was the original implementation of the borrow checker and was part of the initially stabilized Rust 1.0. In mid 2017, work began to implement the current MIR borrow checker and that effort ompleted by the end of 2017, for the most part. During 2018, efforts were made to migrate away from the AST borrow checker to the MIR borrow checker - eventually culminating into "migrate" mode - where HIR typeck with lexical region resolving following by MIR borrow checking - being active by default in the 2018 edition. In early 2019, migrate mode was turned on by default in the 2015 edition as well, but with MIR borrowck errors emitted as warnings. By late 2019, these warnings were upgraded to full errors. This was followed by the complete removal of the AST borrow checker. In the period since, various errors emitted by the MIR borrow checker have been improved to the point that they are mostly the same or better than those emitted by the lexical region resolver. While there do remain some degradations in errors (tracked under the [NLL-diagnostics tag](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-diagnostics), those are sufficiently small and rare enough that increased flexibility of MIR borrow check-only is now a worthwhile tradeoff. ## What is stabilized As said previously, this does not fundamentally change the landscape of accepted programs. However, there are a [few](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-fixed-by-NLL) cases where programs can compile under `feature(nll)`, but not otherwise. There are two notable patterns that are "fixed" by this stabilization. First, the `scoped_threads` feature, which is a continutation of a pre-1.0 API, can sometimes emit a [weird lifetime error](rust-lang/rust#95527) without NLL. Second, actually seen in the standard library. In the `Extend` impl for `HashMap`, there is an implied bound of `K: 'a` that is available with NLL on but not without - this is utilized in the impl. As mentioned before, there are a large number of diagnostic differences. Most of them are better, but some are worse. None are serious or happen often enough to need to block this PR. The biggest change is the loss of error code for a number of lifetime errors in favor of more general "lifetime may not live long enough" error. While this may *seem* bad, the former error codes were just attempts to somewhat-arbitrarily bin together lifetime errors of the same type; however, on paper, they end up being roughly the same with roughly the same kinds of solutions. ## What isn't stabilized This PR does not completely remove the lexical region resolver. In the future, it may be possible to remove that (while still keeping HIR typeck) or to remove it together with HIR typeck. ## Tests Many test outputs get updated by this PR. However, there are number of tests specifically geared towards NLL under `src/test/ui/nll` ## History * On 2017-07-14, [tracking issue opened](rust-lang/rust#43234) * On 2017-07-20, [initial empty MIR pass added](rust-lang/rust#43271) * On 2017-08-29, [RFC opened](rust-lang/rfcs#2094) * On 2017-11-16, [Integrate MIR type-checker with NLL](rust-lang/rust#45825) * On 2017-12-20, [NLL feature complete](rust-lang/rust#46862) * On 2018-07-07, [Don't run AST borrowck on mir mode](rust-lang/rust#52083) * On 2018-07-27, [Add migrate mode](rust-lang/rust#52681) * On 2019-04-22, [Enable migrate mode on 2015 edition](rust-lang/rust#59114) * On 2019-08-26, [Don't downgrade errors on 2015 edition](rust-lang/rust#64221) * On 2019-08-27, [Remove AST borrowck](rust-lang/rust#64790)
Remove migrate borrowck mode Closes #58781 Closes #43234 # Stabilization proposal This PR proposes the stabilization of `#![feature(nll)]` and the removal of `-Z borrowck`. Current borrow checking behavior of item bodies is currently done by first infering regions *lexically* and reporting any errors during HIR type checking. If there *are* any errors, then MIR borrowck (NLL) never occurs. If there *aren't* any errors, then MIR borrowck happens and any errors there would be reported. This PR removes the lexical region check of item bodies entirely and only uses MIR borrowck. Because MIR borrowck could never *not* be run for a compiled program, this should not break any programs. It does, however, change diagnostics significantly and allows a slightly larger set of programs to compile. Tracking issue: #43234 RFC: https://github.com/rust-lang/rfcs/blob/master/text/2094-nll.md Version: 1.63 (2022-06-30 => beta, 2022-08-11 => stable). ## Motivation Over time, the Rust borrow checker has become "smarter" and thus allowed more programs to compile. There have been three different implementations: AST borrowck, MIR borrowck, and polonius (well, in progress). Additionally, there is the "lexical region resolver", which (roughly) solves the constraints generated through HIR typeck. It is not a full borrow checker, but does emit some errors. The AST borrowck was the original implementation of the borrow checker and was part of the initially stabilized Rust 1.0. In mid 2017, work began to implement the current MIR borrow checker and that effort ompleted by the end of 2017, for the most part. During 2018, efforts were made to migrate away from the AST borrow checker to the MIR borrow checker - eventually culminating into "migrate" mode - where HIR typeck with lexical region resolving following by MIR borrow checking - being active by default in the 2018 edition. In early 2019, migrate mode was turned on by default in the 2015 edition as well, but with MIR borrowck errors emitted as warnings. By late 2019, these warnings were upgraded to full errors. This was followed by the complete removal of the AST borrow checker. In the period since, various errors emitted by the MIR borrow checker have been improved to the point that they are mostly the same or better than those emitted by the lexical region resolver. While there do remain some degradations in errors (tracked under the [NLL-diagnostics tag](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-diagnostics), those are sufficiently small and rare enough that increased flexibility of MIR borrow check-only is now a worthwhile tradeoff. ## What is stabilized As said previously, this does not fundamentally change the landscape of accepted programs. However, there are a [few](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-fixed-by-NLL) cases where programs can compile under `feature(nll)`, but not otherwise. There are two notable patterns that are "fixed" by this stabilization. First, the `scoped_threads` feature, which is a continutation of a pre-1.0 API, can sometimes emit a [weird lifetime error](rust-lang/rust#95527) without NLL. Second, actually seen in the standard library. In the `Extend` impl for `HashMap`, there is an implied bound of `K: 'a` that is available with NLL on but not without - this is utilized in the impl. As mentioned before, there are a large number of diagnostic differences. Most of them are better, but some are worse. None are serious or happen often enough to need to block this PR. The biggest change is the loss of error code for a number of lifetime errors in favor of more general "lifetime may not live long enough" error. While this may *seem* bad, the former error codes were just attempts to somewhat-arbitrarily bin together lifetime errors of the same type; however, on paper, they end up being roughly the same with roughly the same kinds of solutions. ## What isn't stabilized This PR does not completely remove the lexical region resolver. In the future, it may be possible to remove that (while still keeping HIR typeck) or to remove it together with HIR typeck. ## Tests Many test outputs get updated by this PR. However, there are number of tests specifically geared towards NLL under `src/test/ui/nll` ## History * On 2017-07-14, [tracking issue opened](rust-lang/rust#43234) * On 2017-07-20, [initial empty MIR pass added](rust-lang/rust#43271) * On 2017-08-29, [RFC opened](rust-lang/rfcs#2094) * On 2017-11-16, [Integrate MIR type-checker with NLL](rust-lang/rust#45825) * On 2017-12-20, [NLL feature complete](rust-lang/rust#46862) * On 2018-07-07, [Don't run AST borrowck on mir mode](rust-lang/rust#52083) * On 2018-07-27, [Add migrate mode](rust-lang/rust#52681) * On 2019-04-22, [Enable migrate mode on 2015 edition](rust-lang/rust#59114) * On 2019-08-26, [Don't downgrade errors on 2015 edition](rust-lang/rust#64221) * On 2019-08-27, [Remove AST borrowck](rust-lang/rust#64790)
As per decision on a language team meeting as described in #63565 (comment), in Rust 2015, we refuse to downgrade NLL errors, that AST borrowck accepts, into warnings and keep them as hard errors.
The remaining work to throw out AST borrowck and adjust some tests still remains after this PR.
Fixes #38899
Fixes #53432
Fixes #45157
Fixes #31567
Fixes #27868
Fixes #47366
r? @matthewjasper