Custom main and global executors work hasn't passed Swift Evolution yet,
so we need to avoid leaking it as API until it does.
To that end, underscore all the things.
rdar://151147606
Dispatch uses unsigned times, and cannot cope with times before its
clock started. As such, passing negative times from Swift through to
the C++ code results in large unsigned values, which then causes us to
wait forever. This is undesirable.
rdar://148899609
This caused a hard-to-reproduce bug where a machine that had slept for
a long time would take a very long time to run some of the tests because
we'd be scheduling Dispatch executions with the wrong clock.
rdar://148337712
EventableExecutor is being removed, for now, but hopefully will
return in some form in the future.
The `asSchedulable` implementation needs to change for reasons of
ABI stability.
rdar://141348916
Remove `supportsScheduling` in favour of a type-based approach.
Update the storage for `ClockTraits` to `UInt32`.
Adjust ordering of executors for `currentExecutor`.
rdar://141348916
Rename `DispatchTaskExecutor` to `DispatchGlobalTaskExecutor` as we
may want to use the former for an executor that runs things on an
arbitrary Dispatch queue.
Rename `DispatchExecutor` to `DispatchExecutorProtocol`; again, we
might want the name for something else.
Add `@Sendable` attribute to `registerEvent`.
Fix missing `extern "C" SWIFT_CC(swift)` on `_swift_exit` (merge
error).
Remove stray whitespace from `CMakeLists.txt`
rdar://141348916
Remove the hacky support for mapping clocks to a Dispatch clock ID,
in favour of clocks publishing traits and having the Dispatch
executor select the clock on the basis of those traits.
Added an `-executor-factory` argument to the compiler to let you safely
specify the executors you wish to use (by naming a type that returns
them).
Also added some tests of the new functionality.
rdar://141348916
Reorganise the Concurrency code so that it's possible to completely
implement executors (both main and global) in Swift.
Provide API to choose the desired executors for your application.
Also make `Task.Sleep` wait using the current executor, not the global
executor, and expose APIs on `Clock` to allow for conversion between
time bases.
rdar://141348916
