Per SE-0411, we compute the isolation of a default value expression
based on what isolation it requires. Include isolated conformance
checks in this computation, rather than always emitting diagnostics,
so that the combination of isolated default values + isolated
conformances works as expected.
Fixes rdar://150691429.
If all of the witnesses to a conformance are nonisolated, then infer that
conformance as nonisolated rather than global-actor-isolated. This is
only relevant when InferIsolatedConformances is enabled, and prevents
that inference to help maintain source compatibility.
The IsolatedConformances feature moves to a normal, supported feature.
Remove all of the experimental-feature flags on test cases and such.
The InferIsolatedConformances feature moves to an upcoming feature for
Swift 7. This should become an adoptable feature, adding "nonisolated"
where needed.
This removes the IsolatedConformances feature gate from SILGen for
dynamic casts, such that all dynamic casts that will not work with
isolated conformances are marked as such. Isolated conformances can
still only come into a program when part of it enables the feature
flag.
