Remove migrate borrowck mode
Closes#58781Closes#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](https://github.com/rust-lang/rust/issues/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](https://github.com/rust-lang/rust/issues/43234)
* On 2017-07-20, [initial empty MIR pass added](https://github.com/rust-lang/rust/pull/43271)
* On 2017-08-29, [RFC opened](https://github.com/rust-lang/rfcs/pull/2094)
* On 2017-11-16, [Integrate MIR type-checker with NLL](https://github.com/rust-lang/rust/pull/45825)
* On 2017-12-20, [NLL feature complete](https://github.com/rust-lang/rust/pull/46862)
* On 2018-07-07, [Don't run AST borrowck on mir mode](https://github.com/rust-lang/rust/pull/52083)
* On 2018-07-27, [Add migrate mode](https://github.com/rust-lang/rust/pull/52681)
* On 2019-04-22, [Enable migrate mode on 2015 edition](https://github.com/rust-lang/rust/pull/59114)
* On 2019-08-26, [Don't downgrade errors on 2015 edition](https://github.com/rust-lang/rust/pull/64221)
* On 2019-08-27, [Remove AST borrowck](https://github.com/rust-lang/rust/pull/64790)
Add build metrics to rustbuild
This PR adds a new module of rustbuild, `ci_profiler`, whose job is to gather as much information as possible about the CI build as possible and store it in a JSON file uploaded to `ci-artifacts`. Right now for each step it collects:
* Type name and debug representation of the `Step` object.
* Duration of the step (excluding child steps).
* Systemwide CPU stats for the duration of the step (both single core and all cores).
* Which child steps were executed.
This is capable of replacing both the scripts to collect CPU stats and the `[TIMING]` lines in build logs (not yet removed, until we port our tooling to use the CI profiler). The format is also extensible to be able in the future to collect more information.
r? `@Mark-Simulacrum`
Add PID to LLVM PGO profile path
This is a continuation of https://github.com/rust-lang/rust/pull/97110, which adds PID to the filename pattern of LLVM profiles. It also adds some metrics to the pgo.sh script, so that we can observe how many profiles there are and how large are they.
r? `@lqd`
Re-add help_on_error for download-ci-llvm
Closes#97503
- Re-added `help_on_error` for `download_component()` and the downstream functions
- Removed dead code in `bootstrap.py`
Thanks `@jyn514` for the helpful tips!
(first contribution here, please let me know if I missed anything out!)
Finish bumping stage0
It looks like the last time had left some remaining cfg's -- which made me think
that the stage0 bump was actually successful. This brings us to a released 1.62
beta though.
This now brings us to cfg-clean, with the exception of check-cfg-features in bootstrap;
I'd prefer to leave that for a separate PR at this time since it's likely to be more tricky.
cc https://github.com/rust-lang/rust/pull/97147#issuecomment-1132845061
r? `@pietroalbini`
Prepare Rust for opaque pointers
Fix one codegen bug with opaque pointers, and update our IR tests to accept both typed pointer and opaque pointer IR. This is a bit annoying, but unavoidable if we want decent test coverage on both LLVM 14 and LLVM 15.
This prepares Rust for when LLVM will enable opaque pointers by default.
Move download-rustc from python to rustbuild
- Remove download-rustc handling from bootstrap.py
- Allow a custom `pattern` in `builder.unpack()`
- Only download rustc once another part of bootstrap depends on it.
This is somewhat necessary since the download functions rely on having a full
`Builder`, which isn't available until after config parsing finishes.
Helps with https://github.com/rust-lang/rust/issues/94829.
[bootstrap] Move `sanitize_sh` from `dist` to `install`
This is the only place it's used, so there's no need for it to be public in another module.
In general, `dist` shouldn't ever touch shell scripts.
Print stderr consistently
Solves https://github.com/rust-lang/rust/issues/96712
I tried to follow what I perceived as the general consensus for error messages in boostrap i.e messages that were ..
* resulting from an Err(...) =>
* literally called as "Error: ...."
* by the end of the block scope forced to run a panic! or process::exit with a guaranteed non-zero error code.
It looks like the last time had left some remaining cfg's -- which made me think
that the stage0 bump was actually successful. This brings us to a released 1.62
beta though.
Only allow `compiletest` to use `feature(test)`, not any other feature
Using language features occasionally causes issues when using nightly to bootstrap, rather than beta.
See #59264 for additional context.
- Remove download-rustc handling from bootstrap.py
- Allow a custom `pattern` in `builder.unpack()`
- Only download rustc once another part of bootstrap depends on it.
This is somewhat necessary since the download functions rely on having a full
`Builder`, which isn't available until after config parsing finishes.
- The logic is now unified for all targets (wasm targets should also be supported now)
- Additional "symlink" files like `ld64` are eliminated
- lld-wrapper is used for propagating the correct lld flavor
- Cleanup "unwrap or exit" logic in lld-wrapper
Turn on `fast_submodules` unconditionally
I don't know why anyone would turn this off; doing so makes builds much slower (nearly a 60x slowdown according to #49057).
Remove the option to do so, which makes bootstrap a little easier to maintain.
Bootstrap continues to allow you to manage submodules manually by setting `submodules = false`.
I don't know why anyone would turn this off; doing so makes builds much slower (nearly a 60x slowdown according to #49057).
Remove the option to do so, which makes bootstrap a little easier to maintain.
Bootstrap continues to allow you to manage submodules manually by setting `submodules = false`.
Avoid accidentally enabling unstable features in compilers (take 2)
This allows rustbuild to control whether crates can use nightly features or not.
It also prevents rustbuild from using nightly features itself.
This is #92261, but I fixed the CI error.
Omit stdarch workspace from rust-src
The path `library/stdarch/crates/Cargo.toml` does not exist.
In Rust 1.61.0, `rust-src` still includes `src/rust/library/stdarch/Cargo.toml` (but not `stdarch-verify`), which includes
```toml
[workspace]
members = [
"crates/stdarch-verify"
```
This didn't show up when testing with `-Zbuild-std` in https://github.com/rust-lang/rust/pull/94907 since the [standard list of crates](f624095e1c/src/cargo/core/compiler/standard_lib.rs (L26-L30)) to include when building `std` does not include `stdarch`, but it will show up if a user explicitly requests `stdarch`. Or, perhaps more importantly, because of https://github.com/rust-lang/rust/issues/95736, many editors (like IntelliJ) won't treat the root of `rust-src` as a workspace, and will instead recurse into all the sub-crates directly, which then includes `stdarch`.
Also related to https://github.com/rust-lang/rust/issues/94906.
Fix `download-ci-llvm` NixOS patching for `.so`s.
See https://github.com/rust-lang/rust/pull/95170#discussion_r872960686 - in short, `Path::ends_with` doesn't do the same thing as `str::ends_with`, and can only be used to check for whole file names, not extensions.
With this PR, I get the full suite of:
```
extracting /home/eddy/Projects/rust-A/build/cache/llvm-ebb80ec4e90f8622440f3e33562db0d6e6c66555-true/rust-dev-nightly-x86_64-unknown-linux-gnu.tar.xz to /home/eddy/Projects/rust-A/build/x86_64-unknown-linux-gnu/ci-llvm
info: you seem to be using Nix. Attempting to patch /home/eddy/Projects/rust-A/build/x86_64-unknown-linux-gnu/ci-llvm/bin/llvm-config
/nix/store/r4bzq2xilvv8fmqjg626hzwi22ah3hf4-rust-stage0-dependencies
info: you seem to be using Nix. Attempting to patch /home/eddy/Projects/rust-A/build/x86_64-unknown-linux-gnu/ci-llvm/bin/FileCheck
info: you seem to be using Nix. Attempting to patch /home/eddy/Projects/rust-A/build/x86_64-unknown-linux-gnu/ci-llvm/lib/libLLVM-14-rust-1.62.0-nightly.so
```
(that `libLLVM-14-rust-1.62.0-nightly.so` at the end having been missing before)
r? `@Mark-Simulacrum` cc `@jyn514`
