Rustdoc does not apply cfg(parallel_compiler) when bootstrapping

[cjgillot]

Found while testing #70951.

I tried this code:

In rustc_middle:

pub trait QueryEngine {
  #[cfg(parallel_compiler)]
  unsafe fn deadlock();
}

In downstream crate rustc_query_system:

impl QueryEngine for QueryCtxt {
  #[cfg(parallel_compiler)]
  unsafe fn deadlock() {}
}

I expected to see this happen: rustdoc run successfully.

Instead, this happened: rustdoc complains of missing impl-item deadlock.

My understanding is that ./x.py check compiles with parallel_compiler = true and
puts the trait with deadcode in its metadata.
Rustdoc tries to document ignoring parallel_compiler,
so the function deadcode is missing.

Meta

master at 8599bff

[jyn514]

My understanding is that cfg(parallel_compiler) applies to rustdoc itself just fine, the issue is that rustdoc ignores the cfg when documenting. Is that correct?

[jyn514]

@cjgillot I can't reproduce this. I ran the following locally:

git checkout b52769b804a12b7045ee1bce893a64045cdb974a  # current HEAD
git revert 9823c2cc700fea541bf2670fcee93af662b63022.
x.py doc compiler/rustc

and all the commands succeeded.

[jyn514]

Oh, I forgot to set parallel-compiler = true. Yes, with that I can reproduce.