Skip to content

add field_of! macro and field representing types #118658

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Closed
wants to merge 1 commit into from
Closed

add field_of! macro and field representing types #118658

wants to merge 1 commit into from

Conversation

BennoLossin
Copy link
Contributor

I implemented the core of rust-lang/rfcs#3318 for personal experimentation and found out that you can get experimental features merged easier than a whole RFC. I do not know the correct process to do this, but I thought a PR would be the way to go.

This PR introduces field info types. These types are generated for every field of every struct. They can be named by using the core::mem::field_of!() macro also introduced by this PR.

I have not had any experience modifying the Rust compiler, so there will be mistakes. I could definitely use some help refining this, so any comments are welcomed. The way I implemented was by first looking at offset_of! then realizing I want something that resolves to a type and not an expression, I then went and took a look at how impl Trait types are implemented and copied a lot from that. At some point I also realized that type equality and trait resolution were incorrect, so I went digging and I think I fixed it.

Here a list of things to complete before even thinking about merging:

  • create an issue to use for the unstability attribute on field_of!
  • handle TODOs in the code
  • bikeshed the name FieldInfo: should the hir version be named FieldOf?
  • how to handle enums/unions?
  • can this also handle slices/arrays?
  • fix type inference, i.e. allow field_of!(_, foo)
  • remove some debugging stuff
  • solve ICEs when using cargo instead of rustc
Example Code 
#![feature(field_project, offset_of)]
use std::mem::{field_of, offset_of, MaybeUninit};

unsafe trait Field {
    type Base;
    type Type;
    const OFFSET: usize;
}

trait Project<F: Field> {
    type Output;
    fn project(self) -> Self::Output;
}

impl<'a, F: Field> Project<F> for &'a mut MaybeUninit<F::Base>
where
    F::Type: 'a,
{
    type Output = &'a mut MaybeUninit<F::Type>;
    fn project(self) -> Self::Output {
        let ptr = self.as_mut_ptr().cast::<u8>().wrapping_add(F::OFFSET);
        unsafe { &mut *ptr.cast() }
    }
}

#[derive(Debug)]
struct Foo {
    value: usize,
    next: Option<Box<Foo>>,
}

unsafe impl Field for field_of!(Foo, value) {
    type Base = Foo;
    type Type = usize;
    const OFFSET: usize = offset_of!(Foo, value);
}

unsafe impl Field for field_of!(Foo, next) {
    type Base = Foo;
    type Type = Option<Box<Foo>>;
    const OFFSET: usize = offset_of!(Foo, next);
}

fn main() {
    let mut foo = MaybeUninit::uninit();
    Project::<field_of!(Foo, value)>::project(&mut foo).write(42);
    Project::<field_of!(Foo, next)>::project(&mut foo).write(Some(Box::new(Foo {
        value: 84,
        next: None,
    })));
    println!("{:?}", unsafe { foo.assume_init_ref() });
}

Output: Foo { value: 42, next: Some(Foo { value: 84, next: None }) }

@rustbot
Copy link
Collaborator

rustbot commented Dec 5, 2023

r? @b-naber

(rustbot has picked a reviewer for you, use r? to override)

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Dec 5, 2023
@rustbot
Copy link
Collaborator

rustbot commented Dec 5, 2023

Some changes occurred to the CTFE / Miri engine

cc @rust-lang/miri

This PR changes Stable MIR

cc @oli-obk, @celinval, @spastorino, @ouz-a

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

@rust-log-analyzer
Copy link
Collaborator

The job mingw-check-tidy failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot) 
Prepare all required actions
Getting action download info
Download action repository 'actions/checkout@v4' (SHA:b4ffde65f46336ab88eb53be808477a3936bae11)
Download action repository 'actions/upload-artifact@v3' (SHA:a8a3f3ad30e3422c9c7b888a15615d19a852ae32)
Complete job name: PR - mingw-check-tidy
git config --global core.autocrlf false
shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}
---
GITHUB_ACTION=__run_7
GITHUB_ACTIONS=true
GITHUB_ACTION_REF=
GITHUB_ACTION_REPOSITORY=
GITHUB_ACTOR=y86-dev
GITHUB_API_URL=https://api.github.com
GITHUB_BASE_REF=master
GITHUB_ENV=/home/runner/work/_temp/_runner_file_commands/set_env_6ada0e6d-a063-4ff0-b924-9aa806e7afd6
GITHUB_EVENT_NAME=pull_request
---
GITHUB_SERVER_URL=https://github.com
GITHUB_SHA=1191f6ebd903863da1bb54607b8891698bea7837
GITHUB_STATE=/home/runner/work/_temp/_runner_file_commands/save_state_6ada0e6d-a063-4ff0-b924-9aa806e7afd6
GITHUB_STEP_SUMMARY=/home/runner/work/_temp/_runner_file_commands/step_summary_6ada0e6d-a063-4ff0-b924-9aa806e7afd6
GITHUB_TRIGGERING_ACTOR=y86-dev
GITHUB_WORKFLOW_REF=rust-lang/rust/.github/workflows/ci.yml@refs/pull/118658/merge
GITHUB_WORKFLOW_SHA=1191f6ebd903863da1bb54607b8891698bea7837
GITHUB_WORKSPACE=/home/runner/work/rust/rust
GOROOT_1_19_X64=/opt/hostedtoolcache/go/1.19.13/x64
---
Removing intermediate container 75fd1c05e799
 ---> e116903969ac
Step 6/10 : COPY host-x86_64/mingw-check/reuse-requirements.txt /tmp/
 ---> 14e1bcc900d0
Step 7/10 : RUN pip3 install --no-deps --no-cache-dir --require-hashes -r /tmp/reuse-requirements.txt     && pip3 install virtualenv
Collecting binaryornot==0.4.4
  Downloading binaryornot-0.4.4-py2.py3-none-any.whl (9.0 kB)
Collecting boolean-py==4.0
  Downloading boolean.py-4.0-py3-none-any.whl (25 kB)
---
Building wheels for collected packages: reuse
  Building wheel for reuse (pyproject.toml): started
  Building wheel for reuse (pyproject.toml): finished with status 'done'
  Created wheel for reuse: filename=reuse-1.1.0-cp310-cp310-manylinux_2_35_x86_64.whl size=180123 sha256=f323ccf11d14c5b11f6d5e70edb46e391f4b49a5df5c7d922224477ad8ee15c5
  Stored in directory: /tmp/pip-ephem-wheel-cache-rc4op7w1/wheels/c2/3c/b9/1120c2ab4bd82694f7e6f0537dc5b9a085c13e2c69a8d0c76d
Installing collected packages: boolean-py, binaryornot, setuptools, reuse, python-debian, markupsafe, license-expression, jinja2, chardet
  Attempting uninstall: setuptools
    Found existing installation: setuptools 59.6.0
    Not uninstalling setuptools at /usr/lib/python3/dist-packages, outside environment /usr
---
  Downloading virtualenv-20.25.0-py3-none-any.whl (3.8 MB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 3.8/3.8 MB 61.6 MB/s eta 0:00:00
Collecting filelock<4,>=3.12.2
  Downloading filelock-3.13.1-py3-none-any.whl (11 kB)
Collecting distlib<1,>=0.3.7
  Downloading distlib-0.3.7-py2.py3-none-any.whl (468 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 468.9/468.9 KB 134.5 MB/s eta 0:00:00
Collecting platformdirs<5,>=3.9.1
  Downloading platformdirs-4.1.0-py3-none-any.whl (17 kB)
Installing collected packages: distlib, platformdirs, filelock, virtualenv
Successfully installed distlib-0.3.7 filelock-3.13.1 platformdirs-4.1.0 virtualenv-20.25.0
Removing intermediate container 298f44070fe9
 ---> acbdfd07fece
Step 8/10 : COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
 ---> 44e51c3b5cbc
 ---> 44e51c3b5cbc
Step 9/10 : COPY host-x86_64/mingw-check/validate-error-codes.sh /scripts/
 ---> 12f3768d27b1
Step 10/10 : ENV SCRIPT TIDY_PRINT_DIFF=1 python2.7 ../x.py test            --stage 0 src/tools/tidy tidyselftest --extra-checks=py:lint
Removing intermediate container 03ba07411967
 ---> 790a811bc59b
Successfully built 790a811bc59b
Successfully tagged rust-ci:latest
Successfully tagged rust-ci:latest
##[endgroup]
Built container sha256:790a811bc59b4b960528a27b8806a5496b056fc52a1048d6228e8a719bbecee5
Uploading finished image sha256:790a811bc59b4b960528a27b8806a5496b056fc52a1048d6228e8a719bbecee5 to https://ci-caches.rust-lang.org/docker/139141a603ff222e98d20ef66f0e4eaedfc4b373e41d302ecff577f90ee0c6cf0cab092d18a8f6a073c88b362b9a680d3b2b6e5c828faaf25d1b853eabb78b1a
IMAGE          CREATED          CREATED BY                                      SIZE      COMMENT
790a811bc59b   1 second ago     /bin/sh -c #(nop)  ENV SCRIPT=TIDY_PRINT_DIF…   0B        
44e51c3b5cbc   2 seconds ago    /bin/sh -c #(nop) COPY file:078ea1d11e7b7cda…   367B      
acbdfd07fece   4 seconds ago    |1 DEBIAN_FRONTEND=noninteractive /bin/sh -c…   23.9MB    
14e1bcc900d0   10 seconds ago   /bin/sh -c #(nop) COPY file:ac591dd6bc5afa66…   5.33kB    
e116903969ac   11 seconds ago   |1 DEBIAN_FRONTEND=noninteractive /bin/sh -c…   23.1MB    
---
<missing>      4 days ago       /bin/sh -c #(nop)  LABEL org.opencontainers.…   0B        
<missing>      4 days ago       /bin/sh -c #(nop)  ARG LAUNCHPAD_BUILD_ARCH     0B        
<missing>      4 days ago       /bin/sh -c #(nop)  ARG RELEASE                  0B        

<botocore.awsrequest.AWSRequest object at 0x7fb6eb6c2d50>
gzip: stdout: Broken pipe
xargs: docker: terminated by signal 13
https://ci-caches.rust-lang.org/docker/139141a603ff222e98d20ef66f0e4eaedfc4b373e41d302ecff577f90ee0c6cf0cab092d18a8f6a073c88b362b9a680d3b2b6e5c828faaf25d1b853eabb78b1a
sha256:790a811bc59b4b960528a27b8806a5496b056fc52a1048d6228e8a719bbecee5
---
DirectMap4k:      182208 kB
DirectMap2M:     7157760 kB
DirectMap1G:    11534336 kB
##[endgroup]
Executing TIDY_PRINT_DIFF=1 python2.7 ../x.py test            --stage 0 src/tools/tidy tidyselftest --extra-checks=py:lint
+ TIDY_PRINT_DIFF=1 python2.7 ../x.py test --stage 0 src/tools/tidy tidyselftest --extra-checks=py:lint
    Finished dev [unoptimized] target(s) in 0.03s
##[endgroup]
downloading https://ci-artifacts.rust-lang.org/rustc-builds-alt/e9013ac0e402ef449c5d00251d687289599137df/rust-dev-nightly-x86_64-unknown-linux-gnu.tar.xz
extracting /checkout/obj/build/cache/llvm-e9013ac0e402ef449c5d00251d687289599137df-true/rust-dev-nightly-x86_64-unknown-linux-gnu.tar.xz to /checkout/obj/build/x86_64-unknown-linux-gnu/ci-llvm
---
##[endgroup]
fmt check
tidy check
tidy: Skipping binary file check, read-only filesystem
##[error]tidy error: /checkout/compiler/rustc_ty_utils/src/sig_types.rs:98: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
removing old virtual environment
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10'
Requirement already satisfied: pip in ./build/venv/lib/python3.10/site-packages (23.3.1)
Collecting black==23.3.0 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 7))
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 1.7/1.7 MB 18.0 MB/s eta 0:00:00
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 1.7/1.7 MB 18.0 MB/s eta 0:00:00
Collecting click==8.1.3 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 34))
  Downloading click-8.1.3-py3-none-any.whl (96 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 96.6/96.6 kB 703.6 kB/s eta 0:00:00
Collecting importlib-metadata==6.7.0 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 38))
  Downloading importlib_metadata-6.7.0-py3-none-any.whl (22 kB)
Collecting mypy-extensions==1.0.0 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 42))
  Downloading mypy_extensions-1.0.0-py3-none-any.whl (4.7 kB)
Collecting packaging==23.1 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 46))
  Downloading packaging-23.1-py3-none-any.whl (48 kB)
Collecting pathspec==0.11.1 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 50))
  Downloading pathspec-0.11.1-py3-none-any.whl (29 kB)
  Downloading pathspec-0.11.1-py3-none-any.whl (29 kB)
Collecting platformdirs==3.6.0 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 54))
  Downloading platformdirs-3.6.0-py3-none-any.whl (16 kB)
Collecting ruff==0.0.272 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 58))
  Downloading ruff-0.0.272-py3-none-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (5.9 MB)
Collecting tomli==2.0.1 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 77))
  Downloading tomli-2.0.1-py3-none-any.whl (12 kB)
Collecting typed-ast==1.5.4 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 81))
  Downloading typed_ast-1.5.4-cp310-cp310-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl (877 kB)
  Downloading typed_ast-1.5.4-cp310-cp310-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl (877 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 877.7/877.7 kB 118.4 MB/s eta 0:00:00
Collecting typing-extensions==4.6.3 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 107))
  Downloading typing_extensions-4.6.3-py3-none-any.whl (31 kB)
Collecting zipp==3.15.0 (from -r /checkout/src/tools/tidy/config/requirements.txt (line 114))
  Downloading zipp-3.15.0-py3-none-any.whl (6.8 kB)
Installing collected packages: zipp, typing-extensions, typed-ast, tomli, ruff, platformdirs, pathspec, packaging, mypy-extensions, click, importlib-metadata, black
Successfully installed black-23.3.0 click-8.1.3 importlib-metadata-6.7.0 mypy-extensions-1.0.0 packaging-23.1 pathspec-0.11.1 platformdirs-3.6.0 ruff-0.0.272 tomli-2.0.1 typed-ast-1.5.4 typing-extensions-4.6.3 zipp-3.15.0
some tidy checks failed
Build completed unsuccessfully in 0:00:59
  local time: Tue Dec  5 23:47:55 UTC 2023
  network time: Tue, 05 Dec 2023 23:47:55 GMT

@ojeda ojeda mentioned this pull request Dec 6, 2023
Open
46 tasks
@bors
Copy link
Collaborator

bors commented Dec 6, 2023

☔ The latest upstream changes (presumably #118679) made this pull request unmergeable. Please resolve the merge conflicts.

@b-naber
Copy link
Contributor

b-naber commented Dec 16, 2023

Can you convert this to a draft PR?

Unfortunately I currently don't have enough time to help you with any of the outstanding implementation problems. Have you tried asking for help on zulip?

@BennoLossin BennoLossin marked this pull request as draft December 16, 2023 18:57
@BennoLossin
Copy link
Contributor Author

Thanks for the info, I will go ask there.

@Dylan-DPC
Copy link
Member

@y86-dev any updates on this pr?

@BennoLossin
Copy link
Contributor Author

currently I am very busy. @nbdd0121 created an improved version some time ago: https://github.com/nbdd0121/rust/tree/field-projection

@Dylan-DPC
Copy link
Member

Closing this in favour of the improved version

@nbdd0121 can you submit a draft pr here with those changes (even if wip) and mention this pr in the description, makes it easier for future tracking.

@Dylan-DPC Dylan-DPC closed this Feb 22, 2024
@Dylan-DPC Dylan-DPC removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Feb 22, 2024
@nyabinary
Copy link

bump @nbdd0121

@BennoLossin BennoLossin deleted the field-projection branch August 15, 2025 09:17
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Reviewers
No reviews
Assignees

@b-naber b-naber

Labels
T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver)
Projects
None yet
Milestone
No milestone
Development

Successfully merging this pull request may close these issues.
7 participants
@BennoLossin @rustbot @rust-log-analyzer @bors @b-naber @Dylan-DPC @nyabinary