Return a pythran expr when interfering the types in a compare node

Cython/Compiler/ExprNodes.py

@@ -12246,7 +12246,13 @@ class PrimaryCmpNode(ExprNode, CmpNode):
     is_memslice_nonecheck = False
 
     def infer_type(self, env):
-        # TODO: Actually implement this (after merging with -unstable).
+        type1 = self.operand1.infer_type(env)
+        type2 = self.operand2.infer_type(env)
+
+        if is_pythran_expr(type1) or is_pythran_expr(type2):
+            if is_pythran_supported_type(type1) and is_pythran_supported_type(type2):
+                return PythranExpr(pythran_binop_type(self.operator, type1, type2))
+
         return py_object_type
 
     def type_dependencies(self, env):