This changes the isIsolatingCurrentContext function to return `Bool?`
and removes all the witness table trickery we did previously to detect
if it was implemented or not. This comes at a cost of trying to invoke
it always, before `checkIsolated`, but it makes for an simpler
implementation and more checkable even by third party Swift code which
may want to ask this question.
Along with the `withSerialExecutor` function, this now enables us to
check the isolation at runtime when we have an `any Actor` e.g. from
`#isolation`.
Updates SE-0471 according to
https://forums.swift.org/t/se-0471-improved-custom-serialexecutor-isolation-checking-for-concurrency-runtime/78834/
review discussions
In embedded mode, we mustn't have references to the C++ library, because
some embedded platforms don't include the C++ library.
Additionally, it's good to avoid use of global operator new and operator
delete, because they can be globally overridden and this has bitten us
in the past.
rdar://137286187
Define `NOMINMAX` and `WIN32_LEAN_AND_MEAN` when including `<Windows.h>`.
Don't export the interface from DLLs.
Make sure we include `<new>` when using placement operator new.
rdar://135380149
`ExecutorHooks.h` is now nothing to do with hooks, so rename it. Also
there are some additional functions it should declare, and a couple of
places where we've slightly messed up the boundary, for instance
`swift_task_asyncMainDrainQueue` was defined in `Task.cpp` rather than
in the executor implementations, which is wrong, so fix that too.
`CooperativeGlobalExecutor.cpp` now builds against the interface from
`ExecutorImpl.h`, rather than including the all the concurrency headers.
rdar://135380149
C++ executor implementations were `#include`ed into `GlobalExecutor.cpp`,
which makes it difficult to replace the global executor when using the
Embedded Concurrency library. Refactor things so that they build into
separate objects, which means replacing them is just a matter of writing
the relevant functions yourself.
rdar://135380149
