Jordan Rose 9888697544 Correctly check access control for a class's generic superclass (#12629) ...

The previous code was too clever in trying to avoid work and missed
the fact that ClassDecl::getSuperclass produces an interface type but
the types in the inheritance clause are contextual types.

This actually successfully built:

- in non-WMO builds with a public subclass and an internal base class,
  because the internal class symbol wouldn't get stripped out.

- in WMO builds with an internal subclass and a private base class,
  because 'private' has no distinction at the linkage level for a WMO
  build.

However, it's highly likely that trying to import a library containing
such types would result in instability (read: compiler and debugger
crashes), and it's clearly a mistake to allow this. (If you can't show
your superclass to a user in a library's generated interface,
something's definitely gone wrong.)

https://bugs.swift.org/browse/SR-6206

2017-11-09 13:29:24 -08:00

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