Remove unused code in cfg_old

[JonathanBrouwer]

r? @jdonszelmann

Fixes one of the todos from #149865

[rustbot]

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann

[jdonszelmann]

this is awesome work! thanks :) Finally getting rid of some old attr code

@bors r+ rollup

[bors]

📌 Commit acea7df has been approved by jdonszelmann

It is now in the queue for this repository.

[matthiaskrgr]

@bors r-
#149905 (comment)

[matthiaskrgr]

@bors try job=aarch64-gnu-llvm-20-2

[rust-bors]

Unknown argument "job". Run @bors2 help to see available commands.

[matthiaskrgr]

@bors2 try jobs=aarch64-gnu-llvm-20-2

[rust-bors]

💔 Test for ea469cb failed: CI. Failed jobs:

• try - aarch64-gnu-llvm-20-2 (web logs, enhanced plaintext logs)

[JonathanBrouwer]

@bors2 try jobs=aarch64-gnu-llvm-20-2

[rust-bors]

⌛ Trying commit 322e0f7 with merge 44d7933…

To cancel the try build, run the command @bors try cancel.

Workflow: https://github.com/rust-lang/rust/actions/runs/20165191266

[JonathanBrouwer]

Why did PR ci not catch that failure btw?

[rust-log-analyzer]

The job aarch64-gnu-llvm-20-2 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

    /checkout/obj/build/aarch64-unknown-linux-gnu/test/error-index.md - Rust_Compiler_Error_Index::E0536::_::Note__this_error_code_is_no_longer_emitted_by_the_compiler_ (line 11285)

test result: FAILED. 1040 passed; 1 failed; 73 ignored; 0 measured; 0 filtered out; finished in 23.83s

Command `/checkout/obj/build/bootstrap/debug/rustdoc -Wrustdoc::invalid_codeblock_attributes -Dwarnings -Znormalize-docs -Z unstable-options --test /checkout/obj/build/aarch64-unknown-linux-gnu/test/error-index.md --test-args ` failed with exit code 101
Created at: src/bootstrap/src/core/builder/mod.rs:1476:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:2774:13

Command has failed. Rerun with -v to see more details.
Bootstrap failed while executing `--stage 2 test --skip tests --skip coverage-map --skip coverage-run --skip library --skip tidyselftest`
Build completed unsuccessfully in 0:37:40
  local time: Fri Dec 12 12:05:15 UTC 2025
  network time: Fri, 12 Dec 2025 12:05:15 GMT
##[error]Process completed with exit code 1.