local lanes = require "lanes".configure{ verbose_errors = true} -- with timers enabled local function foo() local lanes = lanes -- lanes as upvalue end local g = lanes.gen( "*", foo) -- this should raise an error as lanes.timer_lane is a Lane (a non-deep full userdata) local res, err = pcall( g) print( "Generating lane yielded: ", tostring( res), tostring( err))