regression: trait bound not satisfied

[Mark-Simulacrum]

• https://crater-reports.s3.amazonaws.com/beta-1.65-2/beta-2022-10-11/reg/libreplica-0.1.1/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.65-2/beta-2022-10-11/reg/path-planning-0.1.0/log.txt

https://crater-reports.s3.amazonaws.com/beta-1.65-2/beta-2022-10-11/reg/diesel-softdelete-0.1.0/log.txt might also be related but isn't the exact same error.

[compiler-errors]

This regressed in #98900, cc @lcnr - I may take a look at this later today.

[compiler-errors]

The regression in diesel-softdelete is separate and regressed in #100757 cc @ouz-a

[compiler-errors]

I minimized this from path-planning:

pub trait CSpace<const N: usize>: Sized {
    type Traj;
}

pub trait FullTrajectory<T, S1, const N: usize> {}

pub struct Const<const R: usize>;

pub trait Obstacle<CS, const N: usize>
where
    CS: CSpace<N>,
{
    fn trajectory_free<FT, S1>(&self, t: &FT)
    where
        FT: FullTrajectory<CS::Traj, S1, N>;
}

// -----

const N: usize = 4;

struct ObstacleSpace2df32;

impl<CS> Obstacle<CS, N> for ObstacleSpace2df32
where
    CS: CSpace<N>,
{
    fn trajectory_free<TF, S1>(&self, t: &TF)
    where
        TF: FullTrajectory<CS::Traj, S1, N>,
    {}
}

[compiler-errors]

I put up a potential fix in #103279