Explicitly re-allow memoryviews in default argument structs after disallowing...

Explicitly re-allow memoryviews in default argument structs after disallowing them in structs generally.
Closes #2114.

Cython/Compiler/ExprNodes.py

@@ -9114,7 +9114,6 @@ class PyCFunctionNode(ExprNode, ModuleNameMixin):
                 if not arg.default.is_literal:
                     arg.is_dynamic = True
                     if arg.type.is_pyobject:
-                        # FIXME: should we include memory views here?
                         nonliteral_objects.append(arg)
                     else:
                         nonliteral_other.append(arg)
@@ -9152,7 +9151,7 @@ class PyCFunctionNode(ExprNode, ModuleNameMixin):
             for arg in nonliteral_other:
                 entry = scope.declare_var(arg.name, arg.type, None,
                                           Naming.arg_prefix + arg.name,
-                                          allow_pyobject=False)
+                                          allow_pyobject=False, allow_memoryview=True)
                 self.defaults.append((arg, entry))
             entry = module_scope.declare_struct_or_union(
                 None, 'struct', scope, 1, None, cname=cname)

Cython/Compiler/Nodes.py

@@ -795,7 +795,7 @@ class CFuncDeclaratorNode(CDeclaratorNode):
         scope.declare_var(arg_count_member, PyrexTypes.c_int_type, self.pos)
 
         for arg in func_type.args[len(func_type.args) - self.optional_arg_count:]:
-            scope.declare_var(arg.name, arg.type, arg.pos, allow_pyobject=1)
+            scope.declare_var(arg.name, arg.type, arg.pos, allow_pyobject=True, allow_memoryview=True)
 
         struct_cname = env.mangle(Naming.opt_arg_prefix, self.base.name)
 

Cython/Compiler/Symtab.py

@@ -1862,7 +1862,7 @@ class StructOrUnionScope(Scope):
     def declare_var(self, name, type, pos,
                     cname = None, visibility = 'private',
                     api = 0, in_pxd = 0, is_cdef = 0,
-                    allow_pyobject = 0):
+                    allow_pyobject=False, allow_memoryview=False):
         # Add an entry for an attribute.
         if not cname:
             cname = name
@@ -1875,7 +1875,7 @@ class StructOrUnionScope(Scope):
         self.var_entries.append(entry)
         if type.is_pyobject and not allow_pyobject:
             error(pos, "C struct/union member cannot be a Python object")
-        elif type.is_memoryviewslice and not allow_pyobject:
+        elif type.is_memoryviewslice and not allow_memoryview:
             # Memory views wrap their buffer owner as a Python object.
             error(pos, "C struct/union member cannot be a memory view")
         if visibility != 'private':

tests/run/cyfunction_defaults.pyx

@@ -171,6 +171,31 @@ def test_dynamic_defaults_fused():
         print "i", i, "func result", f(1.0), "defaults", get_defaults(f)
 
 
+def test_memoryview_none(const unsigned char[:] b=None):
+    """
+    >>> test_memoryview_none()
+    >>> test_memoryview_none(None)
+    >>> test_memoryview_none(b'abc')
+    97
+    """
+    if b is None:
+        return None
+    return b[0]
+
+
+def test_memoryview_bytes(const unsigned char[:] b=b'xyz'):
+    """
+    >>> test_memoryview_bytes()
+    120
+    >>> test_memoryview_bytes(None)
+    >>> test_memoryview_bytes(b'abc')
+    97
+    """
+    if b is None:
+        return None
+    return b[0]
+
+
 @cython.test_fail_if_path_exists(
     '//NameNode[@entry.in_closure = True]',
     '//NameNode[@entry.from_closure = True]')