[remcob]

> Another example are the async/await syntax.

Besides the GC that is already mentioned, Haskell has lazy evaluation which gives you coroutines for free. Coroutines are more or less synonymous with async, so in Haskell the implementation is a no-op.

From what I read, much of the challenge of adding async to Rust was in designing the coroutine mechanism, which is a substantial language extension.