Function rustc_typeck::outlives::implicit_infer::check_explicit_predicates

pub fn check_explicit_predicates<'tcx>(
    tcx: TyCtxt<'tcx>, 
    def_id: DefId, 
    substs: &[GenericArg<'tcx>], 
    required_predicates: &mut BTreeMap<OutlivesPredicate<GenericArg<'tcx>, Region<'tcx>>, Span>, 
    explicit_map: &mut ExplicitPredicatesMap<'tcx>, 
    ignored_self_ty: Option<Ty<'tcx>>
)

We also have to check the explicit predicates declared on the type.

struct Foo<'a, T> {
    field1: Bar<T>
}

struct Bar<U> where U: 'static, U: Foo {
    ...
}

Here, we should fetch the explicit predicates, which will give us U: 'static and U: Foo. The latter we can ignore, but we will want to process U: 'static, applying the substitution as above.