An async function is a state machine
Calling an async function creates a future; work advances only while that future is polled. Dropping it stops future polling, but side effects completed before the last suspension point remain completed.
rust / LEVEL 4
The retry loop with no budget
EST.40 MIN
01
THEORY / RETRIEVAL
What to restore
- Build a generic async retry loop over Future-producing operations
- Distinguish future cancellation from rollback of completed side effects
Retry counts are part of the API
A retry helper must define whether the number means total attempts or retries after the first call. Using `NonZeroUsize` makes an impossible zero-attempt result unrepresentable when no error value exists yet.
CHECKPOINT
What happens when a caller drops a future while it is waiting between two retry attempts?
02 / IMPLEMENTATION
Implement the contract
Implement `retry` so `attempts` means total calls, success returns immediately, and the final error is returned after the exact budget. Do not require Clone on errors.
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OUTPUT
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