SR-5289: Teach Mirror how to inspect weak, unowned, and unmanaged refs
Correctly reflect weak, unowned, and unmanaged references
to both Swift and Obj-C types (including existential references to
such types) that occur in both Swift class objects and in Swift
structs.
This includes the specific reported case (unowned reference to an
Obj-C object) and several related ones.
Related changes in this PR:
* Tweak internal bitmap used for tracking ownership modifiers
to reject unsupported combinations.
* Move FieldType into ReflectionMirror.mm
FieldType is really just an internal implementation detail
of this one source file, so it does not belong in an ABI header.
* Use TypeReferenceOwnership directly to track field ownership
This avoids bitwise copying of properties and localizes some
of the knowledge about reference ownership
* Generate a top-level "copyFieldContents" from ReferenceStorage.def
Adding new ownership types to ReferenceStorage.def will now
automatically produce calls to `copy*FieldContents` - failure
to provide a suitable implementation will fail the build.
* Add `deallocateBoxForExistentialIn` to match `allocateBoxForExistentialIn`
Caveat: The unit tests are not as strict as I'd like. Attempting to make them
so ran afoul of otherwise-unrelated bugs in dynamic casting.
* SR-5289: Support reflecting weak, unowned, and unmanaged refs
This refactors how we handle reference ownership
when reflecting fields of struct and class objects.
There are now explicit paths for each type of reference
and some simple exhaustiveness checks to fail the build
if a new reference type is added in the future without
updating this logic.
The dumper method dumps:
1. The container's metadata pointer.
2. A pointer to the container's value.
3. Whether or not said value is stored inline in the container.
This provides a general overview that can be used even when working with SIL
code in the debugger by grabbing a pointer to swift Anys and then calling the
c++ any method upon them.
The verifier is intended to be used in conjunction with ASAN for maximum
effect to catch use-after-frees of existential boxes.
While implementing this I refactored some code from ExistentialTypeMetadata into
methods on OpaqueExistentialContainer. ExistentialTypeMetadata just calls these
methods now instead of implementing the code inline.
