(core_stmts, fv_stmts) <- dsCmdDo ids local_vars' env_ids' res_ty stmts body
return (core_stmts, fv_stmts, varSetElems fv_stmts))
(core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids env_ids' stmt
(core_stmts, fv_stmts) <- dsCmdDo ids local_vars' env_ids' res_ty stmts body
return (core_stmts, fv_stmts, varSetElems fv_stmts))
(core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids env_ids' stmt