Very well put, thanks. Explicit promises have very nice, composable behaviors that I'm exploiting all the time, and that have no equivalent in the Lua coroutin

Very well put, thanks. Explicit promises have very nice, composable behaviors that I'm exploiting all the time, and that have no equivalent in the Lua coroutine world. And once you have propagated them around, I think the ergonomics are just fine; I've taken some pretty hairy callback logic that no one could fully understand without careful study and turned it into async/await code that pretty much anyone could follow. I think the implicitness of "this could suspend" does frequently cause serious problems; in Lua this shows up as the dreaded "Attempt to yield across a metamethod C call boundary" [1] bug. Talk about cognitive load! If you're calling C from Lua, and that C code then calls back into Lua, and the latter function yields, you get this error. So you have to be very careful about what is allowed to yield -- and since any function in Lua, at any point in the call stack, can yield, it's easy to accidentally shoot yourself in the foot. [1] http://stackoverflow.com/questions/8459459/lua-coroutine-error-tempt-to-yield-across-metamethod-c-call-boundary http://stackoverflow.com/questions/8459459/lua-coroutine-err...