Boxable async fn


  • Able to easily cause some async functions, blocks, or closures to allocate their stack space lazilly when called (by 'boxing' it)
    • Combined with profiler or other tooling support, this can help to tune the size of futures
  • Boxed async blocks allows particular portions of a function to be boxed, e.g. cold paths

Design notes

Example might be to use a decorator:

fn main() {
async fn foo() { }

This does not have to desugar to -> Box<dyn Future<...>>; it can instead desugar to Box<impl Future>, or perhaps a nominal type to permit recursion.