Recursion limit tripped in doc but not in other profiles

[TaKO8Ki]

The diesel benchmark has been broken in some recent commit: https://perf.rust-lang.org/status.html.

ref: zulip comment

[rylev]

The error seems to be caused #100757 (cc @ouz-a). Curiously, this only happens in doc.

Here's the error:

 Documenting diesel v1.4.8 (/home/rylevick/code/rustc-perf/collector/benchmarks/diesel-1.4.8)
error[E0275]: overflow evaluating the requirement `<_ as query_source::Column>::Table`
    |
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`diesel`)
note: required for `&expression::operators::Eq<_, _>` to implement `insertable::Insertable<_>`
   --> src/expression/operators.rs:376:21
    |
376 | impl<'a, T, Tab, U> Insertable<Tab> for &'a Eq<T, U>

The line where the error triggers is:

impl<'a, T, Tab, U> Insertable<Tab> for &'a Eq<T, U> // <--- HERE
where
    T: Copy,
    Eq<T, &'a U>: Insertable<Tab>,
{
    type Values = <Eq<T, &'a U> as Insertable<Tab>>::Values;

    fn values(self) -> Self::Values {
        Eq::new(self.left, &self.right).values()
    }
}

You can reproduce this issue by:

• cloning the rustc-perf repo
• going to diesel-1.4.8 benchmark in that repo
• installing commit a72b0e79ba45f05b339b45034996086bf10d3c26 using rustup-toolchain-install-master
• running cargo +a72b0e79ba45f05b339b45034996086bf10d3c26 doc

[ouz-a]

How can I run this(rustc-perf repo) via locally built rustc? @rylev

[weiznich]

#100620 might be related as well?

[ouz-a]

That indeed looks related, so #100705 should fix this ?

[rylev]

The comment here also makes it look like #100705 will fix this.

[rylev]

Unfortunately, #100705 did not fix the issue.

Using the build bors creates after merge 983f4da, cargo +983f4daddf238d114c4adc4751c5528fc6695a5a doc leads to the same error as above.

@ouz-a to reproduce this, you just need to clone the rustc-perf repo and cd into collector/benchmarks/diesel-1.4.8. Then run rustup-toolchain-install-master 983f4daddf238d114c4adc4751c5528fc6695a5a and cargo +983f4daddf238d114c4adc4751c5528fc6695a5a doc

[ouz-a]

Thanks, I will try to push a fix today.

[compiler-errors]

I'm just gonna revert my original PR that introduced this overflow until I can create a version that works with diesel, @ouz-a, given the perf regression of my "fix" and the remaining existence of this issue, so don't waste too much time on this.

[ouz-a]

I already found a fix 😅

[jyn514]

cc #81091

[jyn514]

I've started on minimizing this in https://github.com/jyn514/diesel/tree/mangled-diesel-ice, with the goal of removing the rustdoc special casing once I finish #81091. If someone could finish it up that would be extremely helpful - I think it's related to one of the impls on QueryFragment, if I define an identical trait in mod reproduce it doesn't overflow anymore.

You can reproduce the overflow with rustup-toolchain-install-master 983f4daddf238d114c4adc4751c5528fc6695a5a && cargo +983f4daddf238d114c4adc4751c5528fc6695a5a doc -p diesel --no-default-features.