Function rustc_trait_selection::solve::eval_ctxt::select::rematch_unsize

fn rematch_unsize<'tcx>(
    infcx: &InferCtxt<'tcx>,
    goal: Goal<'tcx, TraitPredicate<'tcx>>,
    nested: Vec<PredicateObligation<'tcx>>,
    source: BuiltinImplSource,
    certainty: Certainty
) -> SelectionResult<'tcx, Selection<'tcx>>

The Unsize trait is particularly important to coercion, so we try rematch it. NOTE: This must stay in sync with consider_builtin_unsize_candidate in trait goal assembly in the solver, both for soundness and in order to avoid ICEs.