internal error: entered unreachable code: we captured two identical projections #104649
Labels
C-bug
Category: This is a bug.
I-ICE
Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
Comments
shepmaster
added
I-ICE
|
I will try to reduce this to an MCVE. |
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Changing |
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Minimized it down to 60 lines without any dependencies. Maybe it can be minimized further but it's getting really hard. I've also left a few comments to say what's going on. "Minimized"trait Project {
type Assoc;
}
pub struct Wrap<T>(T);
impl<T> Project for Wrap<T> {
type Assoc = Result<T, ()>;
}
pub trait Stream {
type Item;
fn get_projected<Fut, F>(self, f: F) -> Self::Item
where
F: FnMut(Self::Item) -> Fut,
Self: Sized,
{
loop {}
}
}
pub struct ProjectFnOutput<F>(F);
impl<F> Stream for ProjectFnOutput<F>
where
F: GetFnOutput,
F::Output: Project,
{
type Item = <F::Output as Project>::Assoc;
}
pub trait GetFnOutput {
type Output;
}
impl<T, R> GetFnOutput for T
where
T: FnOnce() -> R,
{
type Output = R;
}
fn main() {
let proj = ProjectFnOutput(|| {
Wrap(
// This is `Result<(), _1>` but since no type annotations are provided the tpye of _1 is unknown.
Ok(()),
)
});
proj.get_projected(|b| async {
// The type of `b` is `Result<Result<(), _1>, ()> where _1 is unknown.
match b {
Ok(Ok(url)) => {}
Err(e) => {}
Ok(Err(e)) => {}
}
});
} |
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This appears to have regressed in Rust 1.64 1.621.631.64 |
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This continues to ICE on beta and nightly |
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I bisected the regression, here is the output of searched nightlies: from nightly-2022-06-24 to nightly-2022-08-05 bisected with cargo-bisect-rustc v0.6.4Host triple: x86_64-pc-windows-msvc cargo bisect-rustc --access=github --regress=ice --start 1.63.0 --end 1.64.0 -- check |
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Out of these #98574 seems the most likely, cc @dingxiangfei2009 |
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Zooming onto |
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Found MVCE: type Result<T, E = Error> = ::core::result::Result<T, E>;
struct Error;
trait ForEach {
type Input;
fn for_each<F, U>(self, f: F)
where
F: FnOnce(Self::Input) -> U;
}
impl<T> ForEach for A<T> {
type Input = T;
fn for_each<F, U>(self, f: F)
where
F: FnOnce(Self::Input) -> U,
{
todo!()
}
}
struct A<T>(T);
fn main() {
let a = A(Result::Ok(Result::Ok(())));
//~^ ERROR type annotations needed
a.for_each(|a: Result<_>| {
let f = || {
match a {
Ok(Ok(a)) => {},
Ok(Err(a)) => {},
Err(a) => {},
}
};
});
}Output from Rust Playground |
dingxiangfei2009
added a commit
to dingxiangfei2009/rust
that referenced
this issue
Nov 27, 2022
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Code
Cargo.lock
Meta
rustc --version --verbose:Error output
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