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exponential blowup when rerunning due to changed provisional results #210

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@lcnr

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@lcnr

Diesel is currently really slow, @petervdonovan provided the following (likely related) minimization on zulip.

pub trait MapsTmf<E> {
    type Tmf;
}

pub struct BoundedNat;
pub struct Pair<L, R>(std::marker::PhantomData<(L, R)>);

pub trait Heap: Sized
+ MapsTmf<BoundedNat>
+ MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>
+ MapsTmf<Pair<Self::LeftOperand, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>
+ MapsTmf<Pair<Self::RightOperand, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>
+ MapsTmf<Pair<Self::Nat, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>
+ MapsTmf<Pair<Self::F, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>
+ MapsTmf<Pair<Self::Plus, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>
+ MapsTmf<Pair<Self::Sum, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>
+ MapsTmf<Pair<<Self as MapsTmf<BoundedNat>>::Tmf, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>
+ MapsTmf<Pair<<Self as MapsTmf<Pair<Self::LeftOperand, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>
+ MapsTmf<Pair<<Self as MapsTmf<Pair<Self::RightOperand, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>
+ MapsTmf<Pair<<Self as MapsTmf<Pair<Self::Nat, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>
+ MapsTmf<Pair<<Self as MapsTmf<Pair<Self::F, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>
+ MapsTmf<Pair<<Self as MapsTmf<Pair<Self::Plus, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>
+ MapsTmf<Pair<<Self as MapsTmf<Pair<Self::Sum, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>
+ MapsTmf<Pair<<Self as MapsTmf<Pair<<Self as MapsTmf<BoundedNat>>::Tmf, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>
+ MapsTmf<<Self as MapsTmf<Pair<<Self as MapsTmf<Pair<Self::Nat, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>>::Tmf>
+ MapsTmf<<Self as MapsTmf<Pair<<Self as MapsTmf<Pair<Self::F, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>>::Tmf>
+ MapsTmf<<Self as MapsTmf<Pair<<Self as MapsTmf<Pair<Self::Plus, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>>::Tmf>
+ MapsTmf<Pair<<Self as MapsTmf<<Self as MapsTmf<Pair<<Self as MapsTmf<Pair<Self::Nat, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>>::Tmf>>::Tmf, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>
+ MapsTmf<Pair<<Self as MapsTmf<<Self as MapsTmf<Pair<<Self as MapsTmf<Pair<Self::F, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>>::Tmf, <Self as MapsTmf<BoundedNat>>::Tmf>>>::Tmf>>::Tmf, <Self as MapsTmf<<Self as MapsTmf<BoundedNat>>::Tmf>>::Tmf>>
{
    // to trigger the perf issue, we do need multiple associated types involved
    // i.e., replacing all of them with Nat makes the issue go away
    type Plus;
    type LeftOperand;
    type RightOperand;
    type F;
    type Sum;
    type Nat;
}

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