When compiling for visionOS, iOS availability attributes are remapped into the
visionOS availability domain automatically. While the version remapping was
being performed correctly, there was a regression that caused the platform name
to be printed incorrectly in many diagnostics. Whenever an iOS version is
remapped to a visionOS version, availability diagnostics will now present
those versions as visionOS versions instead of iOS versions.
Resolves rdar://146293165.
This feature is essentially self-migrating, but fit it into the
migration flow by marking it as migratable, adding
`-strict-memory-safety:migrate`, and introducing a test.
(cherry picked from commit abad2fae0f)
There's a synthesized call to unsafeBitCast(_:to:), which is obvious
unsafe, and is being diagnosed as such. The compiler generates this
call, so have the compiler also generate the `unsafe` around it to
suppress these warnings.
Fixes rdar://151199011.
