GHC Haskell supports a feature called asynchronous (or async) exceptions. Normal, synchronous exceptions are generated by the currently running code from doing something like trying to read a file that doesn't exist. Asynchronous exceptions are generated from a different thread of execution, either another Haskell green thread, or the runtime system itself.
Rust does not have exceptions at all, much less async exceptions. (Yes, panics behave fairly similarly to synchronous exceptions, but we'll ignore those in this context. They aren't relevant.) Rust also doesn't have a green thread-based runtime like Haskell does. There's basically no direct way to compare this async exception concept from Haskell into Rust.
Or, at least, there wasn't. With Tokio, async/.await, executor, tasks, and futures, the story is quite different. A Haskell green thread looks quite a bit like a Rust task. Suddenly there's a timeout function in Tokio. This post is going to compare the Haskell async exception mechanism to whatever powers Tokio's timeout. It's going to look at various trade-offs of the two different approaches. And I'll end with my own personal analysis.
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