rustc ICEs, "expected a `Fn(u64)` closure, found `F`" about rust HOT 4 OPEN

The ICE happens in diagnostics because of a lack of usable name for a suggestion, error: internal compiler error: compiler/rustc_middle/src/ty/mod.rs:2212:13: item_name: no name for DefPath.

It is on stable and started appearing in 1.77, technically becoming visible in #119869 cc @oli-obk as my due diligence, but that likely just bubbled up the issue. The closure error is now emitted multiple times, but that could be the ICE messing with deduplication (the spans are different tho...).

from rust.

Reduced a bit so we can see it's not related to async.

pub trait ContFn<T>: Fn(T) -> Self::Future {
    type Future;
}
impl<T, F> ContFn<T> for F
where
    F: Fn(T),
{
    type Future = ();
}

pub trait SeqHandler {
    type Requires;
    fn process<F: ContFn<Self::Requires>>() -> impl Sized;
}

pub struct ConvertToU64;
impl SeqHandler for ConvertToU64 {
    type Requires = u64;
    fn process<F: ContFn<Self::Requires>>() -> impl Sized {}
}

fn main() {}

from rust.

Whatever is easier for you. People looking at this issue will find it either way, don't worry :)

from rust.

Reduced a bit so we can see it's not related to async.

pub trait ContFn<T>: Fn(T) -> Self::Future {
    type Future;
}
impl<T, F> ContFn<T> for F
where
    F: Fn(T),
{
    type Future = ();
}

pub trait SeqHandler {
    type Requires;
    fn process<F: ContFn<Self::Requires>>() -> impl Sized;
}

pub struct ConvertToU64;
impl SeqHandler for ConvertToU64 {
    type Requires = u64;
    fn process<F: ContFn<Self::Requires>>() -> impl Sized {}
}

fn main() {}

Should I update issue's example to this one?

from rust.