Prefix global helper function name to reduce the risk of naming collisions due to Pythran usage.

Cython/Compiler/PyrexTypes.py

@@ -1474,7 +1474,7 @@ class CType(PyrexType):
 class PythranExpr(CType):
     # Pythran object of a given type
 
-    to_py_function = "to_python_from_expr"
+    to_py_function = "__Pyx_pythran_to_python"
     is_pythran_expr = True
     writable = True
     has_attributes = 1

Cython/Utility/CppSupport.cpp

@@ -50,7 +50,7 @@ static void __Pyx_CppExn2PyErr() {
 /////////////// PythranConversion.proto ///////////////
 
 template <class T>
-auto to_python_from_expr(T &&value) -> decltype(to_python(
+auto __Pyx_pythran_to_python(T &&value) -> decltype(to_python(
       typename pythonic::returnable<typename std::remove_cv<typename std::remove_reference<T>::type>::type>::type{std::forward<T>(value)}))
 {
   using returnable_type = typename pythonic::returnable<typename std::remove_cv<typename std::remove_reference<T>::type>::type>::type;