The concurrency runtime now deploys back to macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, which corresponds to the 5.1 release of the stdlib.
Adjust macro usages accordingly.
The validation-test suite was incorrectly being run without the
concurrency feature enabled, so the tests were disabled. Now that
they're running, they need fixed availability annotations.
Previously, when saving NecessaryBindings for an async function, if a
type that was passed-in happened to be an archetype, a lookup for that
type's conformance would always be done. However, that lookup was not
always necessary or possible such as in the case where both the metadata
and the witness table were provided to the function in an async context.
Here, that is fixed by using the conformance that was seen when
constructing the NecessaryBindings if one is available.
rdar://problem/72397303
