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by fnord123
1359 days ago
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Are we talking about Rust or async/await syntax in the abstract? Async/await syntax is needed if you want to have a `with` block that managed resources across co-routine boundaries. Consider Python's `async with` which will create a resource that is freed when the co-routine leaves the execution context. This is distinct from Java's try-with-resources which doesn't work with async code. So anytime you use `try (TelemetrySpan.start()) { blah.read().andThen(x->send(url);}` it doesn't do what anyone would ever want. Hopefully Loom fixes it. So the async and sync distinction is needed/useful if you have both. |
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I don't see what is the connection between async/await syntax and managing resources. The `with` block is just another mechanism for managing resources - Go has the `defer` statement which runs the deferred function at the end of currently executing function block, providing the equivalent functionality without need for async/await syntax. The `with` blocks could easily be implemented in Go, but Go doesn't like duplicating functionality in the language.
> Consider Python's `async with`
Python is a traditionally synchronous language, so the async/await syntax in Python is necessary if you want to use the async runtime, while still having compatible syntax with the traditional sync runtime.
> So the async and sync distinction is needed/useful if you have both.
Every sync call can be trivially modeled as an async call that is always awaited. If you want to bolt-on async runtime onto a sync runtime, you need async/await syntax. Other than that, I don't see the value it brings to a language at all.