MemoryView slicing contiguity bugfix (GH-2961)

Fixes GH-2941.

Cython/Compiler/ExprNodes.py

@@ -4722,8 +4722,17 @@ class MemoryCopyScalar(MemoryCopyNode):
             code.putln("%s __pyx_temp_slice = %s;" % (slice_decl, self.dst.result()))
             dst_temp = "__pyx_temp_slice"
 
+        force_strided = False
+        indices = self.dst.original_indices
+        for idx in indices:
+            if isinstance(idx, SliceNode) and not (idx.start.is_none and
+                                                   idx.stop.is_none and
+                                                   idx.step.is_none):
+                force_strided = True
+                
         slice_iter_obj = MemoryView.slice_iter(self.dst.type, dst_temp,
-                                               self.dst.type.ndim, code)
+                                               self.dst.type.ndim, code,
+                                               force_strided=force_strided)
         p = slice_iter_obj.start_loops()
 
         if dtype.is_pyobject:

Cython/Compiler/MemoryView.py

@@ -402,8 +402,8 @@ def get_is_contig_utility(contig_type, ndim):
     return utility
 
 
-def slice_iter(slice_type, slice_result, ndim, code):
-    if slice_type.is_c_contig or slice_type.is_f_contig:
+def slice_iter(slice_type, slice_result, ndim, code, force_strided=False):
+    if (slice_type.is_c_contig or slice_type.is_f_contig) and not force_strided:
         return ContigSliceIter(slice_type, slice_result, ndim, code)
     else:
         return StridedSliceIter(slice_type, slice_result, ndim, code)

tests/memoryview/memslice.pyx

@@ -2252,7 +2252,9 @@ def test_contig_scalar_to_slice_assignment():
     """
     >>> test_contig_scalar_to_slice_assignment()
     14 14 14 14
+    30 14 30 14
     20 20 20 20
+    30 30 20 20
     """
     cdef int[5][10] a
     cdef int[:, ::1] m = a
@@ -2260,9 +2262,15 @@ def test_contig_scalar_to_slice_assignment():
     m[...] = 14
     print m[0, 0], m[-1, -1], m[3, 2], m[4, 9]
 
+    m[:, :1] = 30
+    print m[0, 0], m[0, 1], m[1, 0], m[1, 1]
+
     m[:, :] = 20
     print m[0, 0], m[-1, -1], m[3, 2], m[4, 9]
 
+    m[:1, :] = 30
+    print m[0, 0], m[0, 1], m[1, 0], m[1, 1]
+
 @testcase
 def test_dtype_object_scalar_assignment():
     """