Function find_possible_solutions 

pub(crate) fn find_possible_solutions<'genv, 'tcx, Tag>(
    fxctx: &mut FixpointCtxt<'genv, 'tcx, Tag>,
    tag_idx: TagIdx,
    suggestion_ctx: &SuggestionCtxt,
    solver: &mut Option<SuggestionSolver<FixpointTypes>>,
) -> Result<PossibleSolutions, SuggestionSolverError>
where
    Tag: Hash + Eq + Copy,