Fix class ancestry checks for duped classes

Previously in some when classes were duped (specifically those with a
prepended module), they would not correctly have their "superclasses"
array or depth filled in.

This could cause ancestry checks (like is_a? and Module comparisons) to
return incorrect results.

This happened because rb_mod_init_copy builds origin classes in an order
that doesn't have the super linked list fully connected until it's
finished. This commit fixes the previous issue by calling
rb_class_update_superclasses before returning the cloned class. This is
similar to what's already done in make_metaclass.

1 files changed, 2 insertions, 0 deletions

diff --git a/class.c b/class.c
index 39899d5e05..b41e1a37e8 100644
--- a/class.c
+++ b/class.c
@@ -567,6 +567,8 @@ rb_mod_init_copy(VALUE clone, VALUE orig)
         else {
             rb_bug("no origin for class that has origin");
         }
+
+        rb_class_update_superclasses(clone);
     }
 
     return clone;