How to get predicates bound to their types in ImplHeader?

compiler traits working group
1

The following code:

impl<R, K, T: LikeOne> Of<T> for (K, R, i32) 
    where K: LikeTwo {
}

contains ImplHeader:

ImplHeader {    
    impl_def_id: DefId(0:8 ~ marker_with_items[5448]::{impl#1}),
    impl_args: [
        ?0t,
        ?1t,
        ?2t,
    ],
    self_ty: (?0t, ?1t, i32),
    trait_ref: Some(
        <(_, _, i32) as Of<_>>,
    ),
    predicates: [
        Binder { value: TraitPredicate(<_ as std::marker::Sized>, polarity:Positive), bound_vars: [] },
        Binder { value: TraitPredicate(<_ as std::marker::Sized>, polarity:Positive), bound_vars: [] },
        Binder { value: TraitPredicate(<_ as std::marker::Sized>, polarity:Positive), bound_vars: [] },
        Binder { value: TraitPredicate(<_ as LikeOne>, polarity:Positive), bound_vars: [] },   
        Binder { value: TraitPredicate(<_ as LikeTwo>, polarity:Positive), bound_vars: [] },   
    ],
}

but for further analysis I would like to get predicates bound to their generic types. In the end I would like to get 2 lists for trait and for self. Each list contains a generic type and its predicates. The elements of the lists are arranged in the order in which the generic in the corresponding trait and self are arranged. That is: trait: [(T, [LikeOne])] self: [(K, [LikeTwo]), (R, [])]

Or as in ImplHeader:

[
    (?2t, [
        Binder { value: TraitPredicate(<_ as std::marker::Sized>, polarity:Positive), bound_vars: [] },
        Binder { value: TraitPredicate(<_ as LikeOne>, polarity:Positive), bound_vars: [] },
    ])
],
[
    (?0t, [
        Binder { value: TraitPredicate(<_ as std::marker::Sized>, polarity:Positive), bound_vars: [] },
        Binder { value: TraitPredicate(<_ as LikeTwo>>, polarity:Positive), bound_vars: [] },
    ]),
    (?1t, [
        Binder { value: TraitPredicate(<_ as std::marker::Sized>, polarity:Positive), bound_vars: [] }
    ])
]
2

Predicate::kind will give you an enum you can pattern match on to extract basically whatever data you want, although it's not clear what your actual goal is here