Fix const ref temporaries.

Cython/Compiler/Code.py

@@ -626,7 +626,7 @@ class FunctionState(object):
 
         A C string referring to the variable is returned.
         """
-        if type.is_const:
+        if type.is_const and not type.is_reference:
             type = type.const_base_type
         if not type.is_pyobject and not type.is_memoryviewslice:
             # Make manage_ref canonical, so that manage_ref will always mean

tests/run/cpp_template_ref_args.h

@@ -4,6 +4,7 @@
 template <typename T>
 struct Bar {
     Bar & ref() { return *this; }
+    const Bar & const_ref() { return *this; }
     T value;
 };
 

tests/run/cpp_template_ref_args.pyx

@@ -8,6 +8,7 @@ cdef extern from "cpp_template_ref_args.h":
         # bug: Bar[T] created before class fully defined
         T value
         Bar[T] & ref() except +
+        const Bar[T] & const_ref() except +
 
     cdef cppclass Foo[T]:
         Foo()
@@ -33,8 +34,8 @@ def test_template_ref_arg(int x):
 def test_template_ref_attr(int x):
     """
     >>> test_template_ref_attr(4)
-    4
+    (4, 4)
     """
     cdef Bar[int] bar
     bar.value = x
-    return bar.ref().value
+    return bar.ref().value, bar.const_ref().value