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rustc hangs and leaks memory #79714
Description
In stable, rustc 1.48.0 (7eac88abb 2020-11-16), rustc demo.rs promptly returns overflow evaluating the requirement and exits. This is expected behavior.
In nightly, rustc 1.50.0-nightly (5be3f9f10 2020-12-03), rustc demo.rs hangs indefinitely, using 100% of one core. Memory usage fluctuates but tends to grow over time at ~800 MB per minute on my machine.
Source
pub trait Baz {}
impl Baz for () {}
impl<T> Baz for [T; 3] {}
pub trait Fiz {}
impl Fiz for bool {}
pub trait Corge<S> {
type Foo;
}
impl<W: Corge<()>> Corge<[(); 3]> for W {
type Foo = [<W as Corge<()>>::Foo; 3];
}
pub trait Grault
where
Self::B: Fiz,
{
type A;
type B;
}
impl<T: Grault> Grault for [T; 3]
where
Self::A: Baz,
Self::B: Fiz,
{
type A = [T::A; 3];
type B = T::B;
}
pub trait Quaks<S, W> {
fn bar() {}
}
impl<S> Quaks<S, bool> for u8
where
bool: Corge<S>,
<bool as Corge<S>>::Foo: Grault,
{
}
fn main() {
<u8 as Quaks<[(); 3], bool>>::bar();
}rustc --version --verbose:
rustc 1.50.0-nightly (5be3f9f10 2020-12-03)
binary: rustc
commit-hash: 5be3f9f10e9fd59ea03816840a6051413fbdefae
commit-date: 2020-12-03
host: x86_64-unknown-linux-gnu
release: 1.50.0-nightly
Activity
JohnTitor commentedon Dec 5, 2020
This happens on beta as well.
JohnTitor commentedon Dec 5, 2020
The regression introduced between
nightly-2020-10-06(a1dfd24) andnightly-2020-10-07(98edd1f)Possible culprit PRs: #77606, #73905 (UPDATE: confirmed #73905 is the cause)
camelid commentedon Dec 6, 2020
Assigning
P-highand removingI-prioritizeas discussed in the prioritization working group.Mark-Simulacrum commentedon Dec 11, 2020
I am going to move this to P-low as this isn't breaking working code, we have more urgent fall out from #73905 that needs to be fixed first.
[-]rustc nightly hangs and leaks memory[/-][+]rustc hangs and leaks memory[/+]Make recursion limit fatal in project
Prevent caching projections in the case of cycles
Auto merge of rust-lang#80246 - matthewjasper:projection-cycle-cachin…
Make recursion limit fatal in project
Prevent caching projections in the case of cycles
Make recursion limit fatal in project
Prevent caching projections in the case of cycles