`swift-async-algorithms` should be built for Wasm as one of the officially supported platforms on CI to prevent possible future regressions.

…s. (apple#362)

* Correct build failures while updating to 6.2 swift build modes

* Add a package definition for 5.8 builds

* Add some brief explanation for the alteration of the Element in the buffer to an UnsafeTransfer

* Fix broken merge for wasi threads

* Conditionalize the testing targets for non-windows targets to avoid the TaskDriver requirements
* Some driveby formatting fixes and remove the freebsd target since that is not supported in swiftpm yet
* Rework validation import conditions to dependency conditionals
* Exclude 5.9 workflows and enable macOS testing scheme for CI
* Additional ifdefing out non windows targets for sequence diagram testing and more formatting fixes

This is an implementation of share; an algorithm for allowing AsyncSequence types to be iterated by multiple consumers. In addition this cleans up the project to be a starting point for the 1.1 release - it fixes the continuous integration support and configurations but has the cost of only supporting 3 active releases (6.0, 6.1, and 6.2). Previous releases are only going to have legacy support via older released versions.

* Fix the remaining todo on hard cancellation vs soft cancellation

* Update Sources/AsyncAlgorithms/AsyncShareSequence.swift

Co-authored-by: Jamie <[email protected]>

* Update the implementation of share to handle sendability requirements, address some edge cases and update to the latest version of the discussion around buffering behaviors as well as adding some documentation and commentary

* Add some first drafts at unit tests for verifying share behaviors

* Cleanup some of the documentation and address feedback for implementation details

* Fix merge damage by restoring the changes from @jamieQ

* Fix up some availability issues w.r.t. sendable metatypes

* Add a preamble to SendableMetatypes.swift

* Add a fallback for next (for pre 6.2 swift's)

* Slight adjustments for older compiler builds and expose the sendable metatypes since those are part of documentation

* Update formatting and gate availability for older compilers

* Speculative fix for pre 6.1 compiler crashes by removing the sending keyword

* Revert "Speculative fix for pre 6.1 compiler crashes by removing the sending keyword"

This reverts commit 875fa81.

* Speculative fix for pre 6.1 compiler crashes by removing the sending keyword, and correct sendable metatype shim availability

* Remove block comment for formatting check

* Take a more conservative approach and roll back to only supporting share on 6.2

* Only test share on 6.2 or newer

* roll back to older sendable metatype constraints

* yet another stab at 5.10 visionOS guards

* Formatting pass

* Disable 5.10 builds and leave those to older releases

* Ignore swift-version files to avoid local swiftly toolchain selection from being required by others

* Renumber the proposals and copy share into a guide

* Add a link from the primary doc interface to share

---------

Co-authored-by: Jamie <[email protected]>

Signed-off-by: Melissa Kilby <[email protected]>

* Add `AsyncBackpressuredStream` proposal and implementation

# Motivation

The pitch to add external backpressure support to the standard libraries `AsyncStream` got returned for revision since there are larger open questions around `AsyncSequence`. However, having external backpressure in a source asynchronous sequence is becoming more and more important.

# Modification

This PR adds a modified proposal and implementation that brings the Swift Evolution proposal over to Swift Async Algorithms.

* Update proposal and implementation

* Update proposal

* Add example project

* Formatting

* Fix Swift 6.0 build

* Future direction for ~Copyable elements

* Apply formatting

* Fix CI

* Move to 6.1 and update proposal

* Guard tests

* Minor edits to the proposal

* Fix revision order

* FIxup setOnTerminationCallback

* Address review feedback

* Rename to `MultiProducerSingleConsumerAsyncChannel`

* Allow one termination callback per source.

* Fix all sendable warnings

* Remove unbounded strategy, rename copy -> makeAdditionalSource, rename asyncSequence() -> elements(), and move enqueue and cancel to the `CallbackHandle` previously called `CallbackToken`

* Remove Example and fix docs and fix format

* fixes grammar and some word order issues

* Remove unnecessary consume

---------

Co-authored-by: Joe Heck <[email protected]>

….8 so that (apple#377)

symbols that are only available in later versions (for example, MultiProducerSingleConsumerAsyncChannel)
are reflected in the hosted documentation.

…le#380)

`nonisolated(nonsending)` is a 6.2 language feature that allows the inheritance of the callers isolation. The new `MPSCAsyncChannel.Source` send methods should adopt this to avoid unnecessary isolation hops.