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Rust 2015: No longer downgrade NLL errors #64221

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merged 13 commits into from
Sep 27, 2019

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@Centril Centril commented Sep 6, 2019

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

@Centril Centril added T-lang Relevant to the language team, which will review and decide on the PR/issue. relnotes Marks issues that should be documented in the release notes of the next release. labels Sep 6, 2019
@Centril Centril added this to the 1.40 milestone Sep 6, 2019
@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 6, 2019
@Centril Centril added S-blocked Status: Blocked on something else such as an RFC or other implementation work. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 6, 2019
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Centril commented Sep 6, 2019

Marking as blocked on changing nightly to 1.40.

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@Centril Centril force-pushed the nll-no-migrate-2015 branch from 9116ad8 to 5ae30cd Compare September 21, 2019 14:18
@Centril Centril added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-blocked Status: Blocked on something else such as an RFC or other implementation work. labels Sep 25, 2019
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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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@Centril Centril Sep 25, 2019

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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.

// 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.rs Outdated Show resolved Hide resolved
@Centril Centril force-pushed the nll-no-migrate-2015 branch from 5ae30cd to 4503ad4 Compare September 25, 2019 20:10
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Centril commented Sep 25, 2019

Fixed the two currently actionable nits (+ rebased -- don't want to rebuild LLVM :P).

@bors r=matthewjasper

🚀

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bors commented Sep 25, 2019

📌 Commit 4503ad4 has been approved by matthewjasper

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 25, 2019
Centril added a commit to Centril/rust that referenced this pull request Sep 26, 2019
…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
Centril added a commit to Centril/rust that referenced this pull request Sep 26, 2019
…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
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bors commented Sep 26, 2019

📌 Commit 9a2cc54 has been approved by matthewjasper

Centril added a commit to Centril/rust that referenced this pull request Sep 26, 2019
…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
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Centril commented Sep 26, 2019

@bors r=matthewjasper

Carried over @pnkfelix's note in #64790 (comment) to this PR.

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bors commented Sep 26, 2019

📌 Commit 5a0e461 has been approved by matthewjasper

Centril added a commit to Centril/rust that referenced this pull request Sep 26, 2019
…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 added a commit that referenced this pull request Sep 26, 2019
Rollup of 5 pull requests

Successful merges:

 - #64221 ( Rust 2015: No longer downgrade NLL errors)
 - #64772 (Remove tx_to_llvm_workers from TyCtxt)
 - #64783 (Fix issue #64732)
 - #64787 (Fix ExitStatus on Fuchsia)
 - #64812 (Add test for E0543)

Failed merges:

r? @ghost
bors added a commit that referenced this pull request Sep 26, 2019
Rollup of 5 pull requests

Successful merges:

 - #64221 ( Rust 2015: No longer downgrade NLL errors)
 - #64772 (Remove tx_to_llvm_workers from TyCtxt)
 - #64783 (Fix issue #64732)
 - #64787 (Fix ExitStatus on Fuchsia)
 - #64812 (Add test for E0543)

Failed merges:

r? @ghost
@bors bors merged commit 5a0e461 into rust-lang:master Sep 27, 2019
@Centril Centril deleted the nll-no-migrate-2015 branch September 27, 2019 00:19
bors added a commit that referenced this pull request Sep 27, 2019
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)
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Jan 6, 2020
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
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Jan 14, 2020
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
mgeisler added a commit to mgeisler/version-sync that referenced this pull request Mar 30, 2020
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
mgeisler added a commit to mgeisler/version-sync that referenced this pull request Mar 30, 2020
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
mgeisler added a commit to mgeisler/version-sync that referenced this pull request Mar 30, 2020
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
mgeisler added a commit to mgeisler/version-sync that referenced this pull request Mar 30, 2020
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
bors added a commit to rust-lang-ci/rust that referenced this pull request Jun 7, 2022
…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)
flip1995 pushed a commit to flip1995/rust-clippy that referenced this pull request Jun 16, 2022
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)
workingjubilee pushed a commit to tcdi/postgrestd that referenced this pull request Sep 15, 2022
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)
spikespaz pushed a commit to spikespaz/dotwalk-rs that referenced this pull request Aug 29, 2024
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)
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