Regression 1.66 "some_fn::{opaque#0}<'_> does not live long enough"

Code

Unfortunately I couldn't minimize it further without using a dependency (code can be executed online here):

/*
[dependencies]
sycamore = "0.8.2"
web-sys = "0.3"

*/

use sycamore::prelude::{Scope, View, Html, DomNode, ReadSignal, GenericNode};

pub fn create_toggle_bool<'a>(cx: Scope<'a>, initial: bool) -> (&'a ReadSignal<bool>, impl Fn() + Copy + 'a) {
    // let open = sycamore::prelude::create_signal(cx, false);
    // let open_toggle = || open.set(!*open.get());
    // (open, open_toggle)
    (todo!(), || {})
}

pub fn Foo<G: Html>(cx: Scope) -> View<G> {
    let (open, open_toggle) = create_toggle_bool(cx, false);

    // Uncomment these 2 lines to make it compile (moved out of the function)
    // let open = sycamore::prelude::create_signal(cx, false);
    // let open_toggle = || open.set(!*open.get());

    let a = move |_: web_sys::Event| open_toggle();

    move || {
        let __el = DomNode::text_node("test");
        ::sycamore::generic_node::GenericNode::event(&__el, cx, "click", a);
        __el;
    };

    todo!()
}

fn main() {
}

The code compiles and runs with 1.66 but fails with 1.67:

error: `create_toggle_bool::{opaque#0}<'_>` does not live long enough
  --> src/main.rs:28:9
   |
28 |         ::sycamore::generic_node::GenericNode::event(&__el, cx, "click", a);
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I expect this code to still compile on 1.67

Version it worked on

1.66

Version with regression

1.67

rustc 1.67.0 (fc594f156 2023-01-24)
binary: rustc
commit-hash: fc594f15669680fa70d255faec3ca3fb507c3405
commit-date: 2023-01-24
host: x86_64-unknown-linux-gnu
release: 1.67.0
LLVM version: 15.0.6

@rustbot

searched nightlies: from nightly-2022-09-15 to nightly-2022-10-15
regressed nightly: nightly-2022-09-26
searched commit range: 3f83906...f5193a9
regressed commit: f5193a9

bisected with cargo-bisect-rustc v0.6.5

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc --end=2022-10-15

@rustbot label -E-needs-bisection

@rustbot

Minimized to:

use std::marker::PhantomData;
#[derive(Clone, Copy)]
pub struct Scope<'a>(&'a PhantomData<&'a mut &'a ()>);
fn event<'a, F: FnMut() + 'a>(_: Scope<'a>, _: F) {}
fn make_fn<'a>(_: Scope<'a>) -> impl Fn() + Copy + 'a {
    || {}
}

fn foo(cx: Scope) {
    let open_toggle = make_fn(cx);

    || event(cx, open_toggle);
}

fn main() {}

@rustbot label -E-needs-mcve

This is a breaking change but it is a necessary soundness fix

#95474

@oli-obk

Since the crater run there found no regressions I'm gonna @oli-obk anyways but I don't think there's anything to do here.

I only looked at this issue, because there’s been a thread on URLO on a similarly-looking issue that appears to actually regress on 1.67: #107516

Mentioning it here, because it might be of interest to readers of this thread :-)

This is weird, this only broke on my CI because it was pinned to stable (-> 1.67), my local machine was still compiling and running the code fine on 1.66. Maybe the reduced example already regressed in 1.66 but my corner case only regresses in 1.67?

@rustbot

This regression can indeed be mitigated (cc #108691), at least for the MCVE we have.
@rustbot label -A-diagonstics regression-from-stable-to-stable

@rustbot

WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-medium

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Regression 1.66 "`some_fn::{opaque#0}<'_>` does not live long enough" #107426

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Regression 1.66 "some_fn::{opaque#0}<'_> does not live long enough" #107426

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Teapot4195 commented on Jan 28, 2023

clubby789 commented on Jan 28, 2023

clubby789 commented on Jan 28, 2023

Noratrieb commented on Jan 29, 2023

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steffahn commented on Jan 31, 2023

Dav1dde commented on Jan 31, 2023

aliemjay commented on Mar 3, 2023

apiraino commented on Mar 7, 2023

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Regression 1.66 "`some_fn::{opaque#0}<'_>` does not live long enough" #107426