If a package A imports package B, and uses reflect.TypeOf on an unnamed
struct type B.T (such as an alias), we don't want to record B.T's fields
as "do not obfuscate". This is for the same reason that we don't if B.T
is a named struct type: the detection only works for the package
defining the type, as otherwise it's inconsistent.
We failed to handle this case well, because we assumed all struct types
would be under some named type. This is not the case for type aliases.
Fortunately, struct fields are named, and as such they are objects.
Check their package too, just like we do for named types.
Fixes another build error when obfuscating the protobuf module.
We add a simplified version of the example above as a test case,
which originated from debugging the protobuf build failure.
The detection of reflection usage is tricky and there are plenty of edge
cases to test for. We definitely want one script for it, rather than
splitting those cases between other scripts like imports.txt and
syntax.txt.
Moreover, those two were rather generic and large, so this helps keep a
balance.
Daniel Martí