Fix vector to memview cast.

Cython/Compiler/PyrexTypes.py

@@ -4324,6 +4324,8 @@ def c_ptr_type(base_type):
     # Construct a C pointer type.
     if base_type is error_type:
         return error_type
+    elif base_type.is_reference:
+        return CPtrType(base_type.ref_base_type)
     else:
         return CPtrType(base_type)
 

tests/run/memview_vector.pyx

+# mode: run
+# tag: cpp
+
+from libcpp.vector cimport vector
+
+def memview_test(L, int i, int x):
+    """
+    >>> memview_test(range(10), 7, 100)
+    [0, 1, 2, 3, 4, 5, 6, 100, 8, 9]
+    """
+    cdef vector[int] v = L
+    cdef int[::1] mv = <int[:len(L)]> &v[0]
+    mv[i] = x
+    return v