Support memoryviews in PEP-489 notation.

See #2529.

CHANGES.rst

@@ -17,6 +17,9 @@ Features added
   module that can be used for typing in Python code.
   Original patch by Julian Gethmann. (Github issue #1965)
 
+* Memoryviews are supported in PEP-489 style type declarations.
+  (Github issue #2529)
+
 * Raising exceptions from nogil code will automatically acquire the GIL, instead
   of requiring an explicit ``with gil`` block.
 

Cython/Compiler/ExprNodes.py

@@ -3400,10 +3400,21 @@ class IndexNode(_IndexingBaseNode):
                     positional_args=template_values,
                     keyword_args=None)
                 return type_node.analyse(env, base_type=base_type)
+            elif self.index.is_slice or self.index.is_sequence_constructor:
+                # memory view
+                from . import MemoryView
+                axes = [self.index] if self.index.is_slice else list(self.index.args)
+                return PyrexTypes.MemoryViewSliceType(base_type, MemoryView.get_axes_specs(env, axes))
             else:
+                # C array
                 index = self.index.compile_time_value(env)
                 if index is not None:
-                    return PyrexTypes.CArrayType(base_type, int(index))
+                    try:
+                        index = int(index)
+                    except (ValueError, TypeError):
+                        pass
+                    else:
+                        return PyrexTypes.CArrayType(base_type, index)
                 error(self.pos, "Array size must be a compile time constant")
         return None
 

tests/memoryview/memoryview_pep489_typing.pyx

+# mode: run
+# tag: pep489, memoryview
+
+cimport cython
+
+include "../buffers/mockbuffers.pxi"
+
+
+def get_int_2d(mslice: cython.int[:, :], i: cython.int, j: cython.int) -> cython.int:
+    """
+    >>> C = IntMockBuffer("C", range(6), (2,3))
+    >>> get_int_2d(C, 1, 1)
+    acquired C
+    released C
+    4
+
+    Check negative indexing:
+    >>> get_int_2d(C, -1, 0)
+    acquired C
+    released C
+    3
+    >>> get_int_2d(C, -1, -2)
+    acquired C
+    released C
+    4
+    >>> get_int_2d(C, -2, -3)
+    acquired C
+    released C
+    0
+
+    Out-of-bounds errors:
+    >>> get_int_2d(C, 2, 0)
+    Traceback (most recent call last):
+        ...
+    IndexError: Out of bounds on buffer access (axis 0)
+    >>> get_int_2d(C, 0, -4)
+    Traceback (most recent call last):
+        ...
+    IndexError: Out of bounds on buffer access (axis 1)
+    """
+    buf = mslice
+    return buf[i, j]
+
+
+def set_int_2d(mslice: cython.int[:, :], i: cython.int, j: cython.int, value: cython.int) -> cython.int:
+    """
+    Uses get_int_2d to read back the value afterwards. For pure
+    unit test, one should support reading in MockBuffer instead.
+
+    >>> C = IntMockBuffer("C", range(6), (2,3))
+    >>> set_int_2d(C, 1, 1, 10)
+    acquired C
+    released C
+    >>> get_int_2d(C, 1, 1)
+    acquired C
+    released C
+    10
+
+    Check negative indexing:
+    >>> set_int_2d(C, -1, 0, 3)
+    acquired C
+    released C
+    >>> get_int_2d(C, -1, 0)
+    acquired C
+    released C
+    3
+
+    >>> set_int_2d(C, -1, -2, 8)
+    acquired C
+    released C
+    >>> get_int_2d(C, -1, -2)
+    acquired C
+    released C
+    8
+
+    >>> set_int_2d(C, -2, -3, 9)
+    acquired C
+    released C
+    >>> get_int_2d(C, -2, -3)
+    acquired C
+    released C
+    9
+
+    Out-of-bounds errors:
+    >>> set_int_2d(C, 2, 0, 19)
+    Traceback (most recent call last):
+        ...
+    IndexError: Out of bounds on buffer access (axis 0)
+    >>> set_int_2d(C, 0, -4, 19)
+    Traceback (most recent call last):
+        ...
+    IndexError: Out of bounds on buffer access (axis 1)
+
+    """
+    buf = mslice
+    buf[i, j] = value