A lazy property setter stores a value to the underlying storage
of the lazy property. The underlying storage is private, and it
is not proper for a public transparent function body to reference
a private member.
In practice, this only failed if the private member had a
non-constant offset, which only occurs with subclasses of @objc
classes, and resilient classes.
For @objc classes we already had a workaround where no accessors
for stored properties are ever transparent. I put this in to fix
this very issue with lazy properties, but now I realize it was
the wrong workaround, because we still had this problem with
resilient classes.
Note that I'm keeping the logic which made @objc accessors
non-transparent in place, because there's a good chance we will
decide that field offset globals should always be private.
Also, to make this issue reproducible in the test, I changed the
resilience execution tests to build the resilient library as a
dylib and link against that instead of just linking .o files
together. This is because .o files can see each other's internal
symbols, so I was not able to reproduce the original failure
this way. I went ahead and updated the other resilient tests to
do this as well. Also, each test now builds in WMO and non-WMO
mode, to exercise different SIL linking behavior. Again, the
WMO variant was needed to reproduce the issue fixed by this
commit, because without WMO we currently discard serialized SIL,
so no cross-module inlining of the lazy property setter was
taking place.
One minor revision: this lifts the proposed restriction against
overriding a non-open method with an open one. On reflection,
that was inconsistent with the existing rule permitting non-public
methods to be overridden with public ones. The restriction on
subclassing a non-open class with an open class remains, and is
in fact consistent with the existing access rule.
Looks like subclassing classes with resiliently-sized properties works,
as long as the subclass is @_fixed_layout, so let's ensure that's tested.
We don't want @_fixed_layout classes to be a thing though, and we still
can't handle changes to the number of stored properties in a base class,
so a couple of tests are disabled until I land some more patches.
We've already got -enable-resilience and @_fixed_layout to compare
IRGen differences when lowering super_method instructions, so nuke
the -force-resilient-super-dispatch testing flag. While
we're at it, consolidate the super tests a bit.
