tbkka fdb1926421 [SR-5289] Teach Mirror how to handle unowned/unmanaged references (#28823) ...

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.

2019-12-17 09:42:52 -08:00

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