Turn the copy of a read-only memory view always into a writable memory view.

Closes #2134.

1 files changed, 12 insertions, 6 deletions

diff --git a/Cython/Compiler/MemoryView.py b/Cython/Compiler/MemoryView.py
index 77ef59c9d..6ac1d88e4 100644
--- a/Cython/Compiler/MemoryView.py
+++ b/Cython/Compiler/MemoryView.py
@@ -484,18 +484,23 @@ def copy_c_or_fortran_cname(memview):
     return "__pyx_memoryview_copy_slice_%s_%s" % (
             memview.specialization_suffix(), c_or_f)
 
+
 def get_copy_new_utility(pos, from_memview, to_memview):
-    if from_memview.dtype != to_memview.dtype:
-        return error(pos, "dtypes must be the same!")
+    if (from_memview.dtype != to_memview.dtype and
+            not (from_memview.dtype.is_const and from_memview.dtype.const_base_type == to_memview.dtype)):
+        error(pos, "dtypes must be the same!")
+        return
     if len(from_memview.axes) != len(to_memview.axes):
-        return error(pos, "number of dimensions must be same")
+        error(pos, "number of dimensions must be same")
+        return
     if not (to_memview.is_c_contig or to_memview.is_f_contig):
-        return error(pos, "to_memview must be c or f contiguous.")
+        error(pos, "to_memview must be c or f contiguous.")
+        return
 
     for (access, packing) in from_memview.axes:
         if access != 'direct':
-            return error(
-                    pos, "cannot handle 'full' or 'ptr' access at this time.")
+            error(pos, "cannot handle 'full' or 'ptr' access at this time.")
+            return
 
     if to_memview.is_c_contig:
         mode = 'c'
@@ -516,6 +521,7 @@ def get_copy_new_utility(pos, from_memview, to_memview):
             dtype_is_object=int(to_memview.dtype.is_pyobject)),
         requires=[copy_contents_new_utility])
 
+
 def get_axes_specs(env, axes):
     '''
     get_axes_specs(env, axes) -> list of (access, packing) specs for each axis.