fix compiler crash due to uninitialised attribute

Cython/Compiler/ExprNodes.py

@@ -11330,6 +11330,7 @@ class PrimaryCmpNode(ExprNode, CmpNode):
     def analyse_cpp_comparison(self, env):
         type1 = self.operand1.type
         type2 = self.operand2.type
+        self.is_pycmp = False
         entry = env.lookup_operator(self.operator, [self.operand1, self.operand2])
         if entry is None:
             error(self.pos, "Invalid types for '%s' (%s, %s)" %
@@ -11345,7 +11346,6 @@ class PrimaryCmpNode(ExprNode, CmpNode):
         else:
             self.operand1 = self.operand1.coerce_to(func_type.args[0].type, env)
             self.operand2 = self.operand2.coerce_to(func_type.args[1].type, env)
-        self.is_pycmp = False
         self.type = func_type.return_type
 
     def analyse_memoryviewslice_comparison(self, env):

tests/errors/cpp_comparison.pyx

+# mode: error
+# tag: cpp
+
+from libcpp.vector cimport vector
+
+def vector_is_none(vector[int] iv):
+    # TODO: this isn't strictly wrong, so it might be allowed as a 'feature' at some point
+    if iv is None:
+        pass
+
+
+_ERRORS = """
+8:10: Invalid types for 'is' (vector[int], Python object)
+"""