[WIP] Unify AST Visitors with a macro like MIR Visitors

[maxcabrajac]

This is WIP PR to work on #127615

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @lcnr (or someone else) some time within the next two weeks.

Please see the contribution instructions for more information. Namely, in order to ensure the minimum review times lag, PR authors and assigned reviewers should ensure that the review label (S-waiting-on-review and S-waiting-on-author) stays updated, invoking these commands when appropriate:

• @rustbot author: the review is finished, PR author should check the comments and take action accordingly
• @rustbot review: the author is ready for a review, this PR will be queued again in the reviewer's queue

[lcnr]

r? compiler

[lcnr]

r? @cjgillot woops

[cjgillot]

Wow, that's some great work you did @maxcabrajac!
Please take this as an opportunity to simplify stuff. If some distinction has you make weird corner cases, don't hesitate to remove it. My comments are suggestions in this direction.

[cjgillot]

Should we remove the P! from all these?

[maxcabrajac]

I put these P! to maintain all function signatures the same, thus avoiding changes on implementers. I don't know why the original MutVisitor received &mut P<T> instead of &mut T for these types, but I just kept what was being done.

[maxcabrajac]

I think it's better to do two passes. Do what can be done without changing the trait API, after that, change what is weird about their original implementation and change all implementers accordingly. What do you think about it?
There is a pretty big roadblock now... Everything around walk_item seems to be pretty different from Visitor to MutVisitor and I really don't know where to start =/. Do you have any advice on that?

[rust-log-analyzer]

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)

COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
COPY host-x86_64/mingw-check/validate-error-codes.sh /scripts/

# NOTE: intentionally uses python2 for x.py so we can test it still works.
# validate-toolstate only runs in our CI, so it's ok for it to only support python3.
ENV SCRIPT TIDY_PRINT_DIFF=1 python2.7 ../x.py test \
           --stage 0 src/tools/tidy tidyselftest --extra-checks=py:lint,cpp:fmt
# This file is autogenerated by pip-compile with Python 3.10
# by the following command:
#
#    pip-compile --allow-unsafe --generate-hashes reuse-requirements.in
---
#13 2.878 Building wheels for collected packages: reuse
#13 2.879   Building wheel for reuse (pyproject.toml): started
#13 3.131   Building wheel for reuse (pyproject.toml): finished with status 'done'
#13 3.132   Created wheel for reuse: filename=reuse-4.0.3-cp310-cp310-manylinux_2_35_x86_64.whl size=132715 sha256=dfa09868353292d98f811d3efdb0d54d07389e808efc71d68e3b93c514bf8bec
#13 3.133   Stored in directory: /tmp/pip-ephem-wheel-cache-4qkeqtmt/wheels/3d/8d/0a/e0fc6aba4494b28a967ab5eaf951c121d9c677958714e34532
#13 3.135 Installing collected packages: boolean-py, binaryornot, tomlkit, reuse, python-debian, markupsafe, license-expression, jinja2, chardet, attrs
#13 3.537 Successfully installed attrs-23.2.0 binaryornot-0.4.4 boolean-py-4.0 chardet-5.2.0 jinja2-3.1.4 license-expression-30.3.0 markupsafe-2.1.5 python-debian-0.1.49 reuse-4.0.3 tomlkit-0.13.0
#13 3.538 WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
#13 4.080 Collecting virtualenv
#13 4.080 Collecting virtualenv
#13 4.121   Downloading virtualenv-20.26.4-py3-none-any.whl (6.0 MB)
#13 4.200      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 6.0/6.0 MB 78.2 MB/s eta 0:00:00
#13 4.261 Collecting platformdirs<5,>=3.9.1
#13 4.264   Downloading platformdirs-4.3.2-py3-none-any.whl (18 kB)
#13 4.305 Collecting filelock<4,>=3.12.2
#13 4.331 Collecting distlib<1,>=0.3.7
#13 4.334   Downloading distlib-0.3.8-py2.py3-none-any.whl (468 kB)
#13 4.341      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 468.9/468.9 KB 93.0 MB/s eta 0:00:00
#13 4.341      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 468.9/468.9 KB 93.0 MB/s eta 0:00:00
#13 4.421 Installing collected packages: distlib, platformdirs, filelock, virtualenv
#13 4.613 Successfully installed distlib-0.3.8 filelock-3.16.0 platformdirs-4.3.2 virtualenv-20.26.4
#13 DONE 4.7s

#14 [7/8] COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
#14 DONE 0.1s
---
DirectMap4k:      231360 kB
DirectMap2M:     7108608 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,cpp:fmt
+ TIDY_PRINT_DIFF=1 python2.7 ../x.py test --stage 0 src/tools/tidy tidyselftest --extra-checks=py:lint,cpp:fmt
    Finished `dev` profile [unoptimized] target(s) in 0.04s
##[endgroup]
downloading https://ci-artifacts.rust-lang.org/rustc-builds-alt/f7f8bdf2e03918cc3742db3bb37b7cfe9994dbec/rust-dev-nightly-x86_64-unknown-linux-gnu.tar.xz
extracting /checkout/obj/build/cache/llvm-f7f8bdf2e03918cc3742db3bb37b7cfe9994dbec-true/rust-dev-nightly-x86_64-unknown-linux-gnu.tar.xz to /checkout/obj/build/x86_64-unknown-linux-gnu/ci-llvm
---
fmt check
fmt: checked 5538 files
tidy check
tidy: Skipping binary file check, read-only filesystem
##[error]tidy error: /checkout/compiler/rustc_ast/src/visitors.rs:1271: 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 (24.2)
All checks passed!
checking C++ file formatting
some tidy checks failed
some tidy checks failed
Command has failed. Rerun with -v to see more details.
  local time: Wed Sep 11 18:51:54 UTC 2024
  network time: Wed, 11 Sep 2024 18:51:55 GMT
##[error]Process completed with exit code 1.
Post job cleanup.