Cargo fix --edition leads to "error: overflow while checking ... requires drop"

[Renmusxd]

Problem

Running cargo fix --edition on the crate qip=0.15.3 leads to an error:

$ cargo fix --edition
    Checking qip v0.15.3 (.../git/RustQIP)
   Migrating src/lib.rs from 2018 edition to 2021
error: overflow while checking whether `feynman_state::state::FeynmanState<P>` requires drop

error: could not compile `qip` due to previous error
warning: build failed, waiting for other jobs to finish...
error: overflow while checking whether `FeynmanState<P>` requires drop

error: build failed

Building and running cargo check on either edition works fine however.

I will try to make a simplified minimal example soon but needed to run and figured I'd report this then come back to it.

Thanks for all the work on the new version!

Steps

1. Download crate from github
   • Updated/Reduced repo
2. Run cargo fix --edition

Possible Solution(s)

No response

Notes

No response

Version

cargo 1.56.0 (4ed5d137b 2021-10-04)
release: 1.56.0
commit-hash: 4ed5d137baff5eccf1bae5a7b2ae4b57efad4a7d
commit-date: 2021-10-04

[ehuss]

Thanks for the report! I have transferred this to the rust-lang/rust repository since this is a rustc error.

This is similar to #90142, though I'm surprised to not see an ICE message. This may also be related to #90024, though I'm not sure.

Whatever you can do to construct a simplified repro would be appreciated.

cc @rust-lang/wg-rfc-2229

[Renmusxd]

Creating a new main.rs file with feynman_state::state::FeynmanState<P> and all its dependencies does not reproduce the error. I will need to clone the whole file structure and trim things off one at a time. This may take a little while - sorry.

[Renmusxd]

Here's a working example in a single file, turns out it wouldn't reproduce the bug in a main.rs file but does reproduce in a lib.rs:

https://github.com/Renmusxd/RustQIP_ICE

[lqd]

I had the very similar

#![warn(rust_2021_incompatible_closure_captures)]

struct Complex<T>(T);
pub struct FeynmanState<P> {
    _substate: Vec<Vec<Complex<P>>>,
}
impl<P> FeynmanState<P> {
    pub fn calculate_amplitude(&self) -> () {
        todo!()
    }
    pub fn into_state(self) {
        || self.calculate_amplitude();
    }
}

fn main() {
}

It's probably from

rust/compiler/rustc_ty_utils/src/needs_drop.rs

Line 93 in 05044c2

&format!("overflow while checking whether `{}` requires drop", self.query_ty),

[camelid]

Note that it doesn't ICE, and thus there are no backtrace, but it's probably from

@lqd If you pass -Z treat-err-as-bug it should give you a backtrace :)

[lqd]

@camelid I know, this was keeping the reproduction the same as the OP: via cargo fix. To turn this into a rustc failure, or UI test, you'd need to also warn on rust_2021_incompatible_closure_captures or use some of the flags it passes rustc.

[camelid]

@lqd Ah, I see 👍

[JakobDegen]

This is indeed a duplicate of #90024