prevent default arguments from unnecessarily ending up in closures

Cython/Compiler/Visitor.py

@@ -361,6 +361,18 @@ class EnvTransform(CythonTransform):
             self.visitchildren(node)
         return node
 
+    def visit_CArgDeclNode(self, node):
+        # default arguments are evaluated in the outer scope
+        if node.default:
+            attrs = [ attr for attr in node.child_attrs if attr != 'default' ]
+            self.visitchildren(node, attrs)
+            self.env_stack.append((node, self.current_env().outer_scope))
+            self.visitchildren(node, ('default',))
+            self.env_stack.pop()
+        else:
+            self.visitchildren(node)
+        return node
+
 
 class MethodDispatcherTransform(EnvTransform):
     """

tests/run/closure_defaultargs.pyx

+# mode: run
+# tag: closures
+
+cimport cython
+
+@cython.test_fail_if_path_exists(
+    '//NameNode[@entry.in_closure = True]',
+    '//NameNode[@entry.from_closure = True]')
+def test_func_default():
+    """
+    >>> func = test_func_default()
+    >>> func()
+    1
+    >>> func(2)
+    2
+    """
+    def default():
+        return 1
+    def func(arg=default()):
+        return arg
+    return func