Make sure that version dependent special methods are correctly and completely...

Make sure that version dependent special methods are correctly and completely excluded via preprocessor guards.
Previously, implementing "__div__" could fail in Py3 (if the code for adapting the Python wrapper was generated) or would at least generate C compiler warnings about unused "__div__" C functions.

Cython/Compiler/TypeSlots.py

@@ -515,8 +515,8 @@ class BinopSlot(SyntheticSlot):
         SyntheticSlot.__init__(
                 self, slot_name, [left_method, right_method], "0", is_binop=True, **kargs)
         # MethodSlot causes special method registration.
-        self.left_slot = MethodSlot(signature, "", left_method)
-        self.right_slot = MethodSlot(signature, "", right_method)
+        self.left_slot = MethodSlot(signature, "", left_method, **kargs)
+        self.right_slot = MethodSlot(signature, "", right_method, **kargs)
 
 
 class RichcmpSlot(MethodSlot):

tests/run/binop_reverse_methods_GH2056.pyx

 cimport cython
 
+import sys
+IS_PYTHON2 = sys.version_info[0] == 2
+
+__doc__ = ""
+
+
 @cython.c_api_binop_methods(False)
 @cython.cclass
 class Base(object):
@@ -57,6 +63,7 @@ class Base(object):
     def __repr__(self):
         return "%s()" % (self.__class__.__name__)
 
+
 @cython.c_api_binop_methods(False)
 @cython.cclass
 class OverloadLeft(Base):
@@ -128,6 +135,7 @@ class OverloadRight(Base):
         else:
             return NotImplemented
 
+
 @cython.c_api_binop_methods(True)
 @cython.cclass
 class OverloadCApi(Base):
@@ -167,4 +175,84 @@ class OverloadCApi(Base):
         else:
             return NotImplemented
 
+
+if sys.version_info >= (3, 5):
+    __doc__ += """
+    >>> d = PyVersionDependent()
+    >>> d @ 2
+    9
+    >>> 2 @ d
+    99
+    >>> i = d
+    >>> i @= 2
+    >>> i
+    999
+"""
+
+
+@cython.c_api_binop_methods(False)
+@cython.cclass
+class PyVersionDependent:
+    """
+    >>> d = PyVersionDependent()
+    >>> d / 2
+    5
+    >>> 2 / d
+    2
+    >>> d // 2
+    55
+    >>> 2 // d
+    22
+    >>> i = d
+    >>> i /= 2
+    >>> i
+    4
+    >>> i = d
+    >>> i //= 2
+    >>> i
+    44
+    """
+    def __div__(self, other):
+        assert IS_PYTHON2
+        return 5
+
+    def __rdiv__(self, other):
+        assert IS_PYTHON2
+        return 2
+
+    def __idiv__(self, other):
+        assert IS_PYTHON2
+        return 4
+
+    def __truediv__(self, other):
+        assert not IS_PYTHON2
+        return 5
+
+    def __rtruediv__(self, other):
+        assert not IS_PYTHON2
+        return 2
+
+    def __itruediv__(self, other):
+        assert not IS_PYTHON2
+        return 4
+
+    def __floordiv__(self, other):
+        return 55
+
+    def __rfloordiv__(self, other):
+        return 22
+
+    def __ifloordiv__(self, other):
+        return 44
+
+    def __matmul__(self, other):
+        return 9
+
+    def __rmatmul__(self, other):
+        return 99
+
+    def __imatmul__(self, other):
+        return 999
+
+
 # TODO: Test a class that only defines the `__r...__()` methods.