test case for subclasses and vtables

tests/run/subclasses.pyx

+__doc__ = u"""
+>>> zoo = Zoo()
+>>> for cl in (Zoo, Bam, Bar, Foo, Base, Base0): assert isinstance(zoo, cl)
+>>> fooit(zoo)
+42
+
+>>> bam = Bam()
+>>> for cl in (Bam, Bar, Foo, Base, Base0): assert isinstance(bam, cl)
+>>> fooit(bam)
+42
+
+>>> bar = Bar()
+>>> for cl in (Bar, Foo, Base, Base0): assert isinstance(bar, cl)
+>>> fooit(bar)
+42
+
+>>> foo = Foo()
+>>> for cl in (Foo, Base, Base0): assert isinstance(foo, cl)
+>>> fooit(foo)
+42
+
+>>> base = Base()
+>>> for cl in (Base, Base0): assert isinstance(base, cl)
+>>> fooit(base)
+Traceback (most recent call last):
+TypeError: Argument 'foo' has incorrect type (expected subclasses.Foo, got subclasses.Base)
+
+>>> base0 = Base0()
+>>> for cl in (Base0,): assert isinstance(base0, cl)
+>>> fooit(base0)
+Traceback (most recent call last):
+TypeError: Argument 'foo' has incorrect type (expected subclasses.Foo, got subclasses.Base0)
+"""
+
+cdef class Base0:
+    pass
+
+cdef class Base(Base0):
+    pass
+
+cdef class Foo(Base):
+   cdef fooit(self):
+       return 42
+
+cdef class Bar(Foo):
+   pass
+
+cdef class Bam(Bar):
+   pass
+
+cdef class Zoo(Bam):
+   pass
+
+
+def fooit(Foo foo):
+    return foo.fooit()