expr_fvs (Var var) fv_cand in_scope acc = FV.unitFV var fv_cand in_scope acc
expr_fvs (Var var) fv_cand in_scope acc = FV.unitFV var fv_cand in_scope acc
expr_fvs (Var var) fv_cand in_scope acc = FV.unitFV var fv_cand in_scope acc