task: relax 'static bound in LocalSet::block_on
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Currently, `tokio::task::LocalSet`'s `block_on` method requires the future to live for the 'static lifetime. However, this bound is not required — the future is wrapped in a `LocalFuture`, and then passed into `Runtime::block_on`, which does _not_ require a `'static` future. This came up while updating `tokio-compat` to work with version 0.2. To mimic the behavior of `tokio` 0.1's `current_thread::Runtime::run`, we want to be able to have a runtime block on the `recv` future from an mpsc channel indicating when the runtime is idle. To support `!Send` futures, as the old `current_thread::Runtime` did, we must do so inside of a `LocalSet`. However, with the current bounds, we cannot await an `mpsc::Receiver`'s `recv` future inside the `LocalSet::block_on` call. This branch removes the unnecessary `'static` bound. Signed-off-by: Eliza Weisman <[email protected]>
LucioFranco
approved these changes
Dec 2, 2019
Matthias247
approved these changes
Dec 3, 2019
|
@carllerche Lucio pointed out on discord that this is a subtractive API change, so it could potentially be breaking — I can't really see any scenario where it could be a breaking change, but I wanted to see if you had any input? |
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Motivation
Currently,
tokio::task::LocalSet'sblock_onmethod requires thefuture to live for the 'static lifetime. However, this bound is not
required — the future is wrapped in a
LocalFuture, and then passedinto
Runtime::block_on, which does not require a'staticfuture.This came up while updating
tokio-compatto work with version 0.2. Tomimic the behavior of
tokio0.1'scurrent_thread::Runtime::run, wewant to be able to have a runtime block on the
recvfuture from anmpsc channel indicating when the runtime is idle. To support
!Sendfutures, as the old
current_thread::Runtimedid, we must do so insideof a
LocalSet. However, with the current bounds, we cannot await anmpsc::Receiver'srecvfuture inside theLocalSet::block_oncall.Solution
This branch removes the unnecessary
'staticbound.Signed-off-by: Eliza Weisman [email protected]