Handle function "outer_attrs" more consistently (GH-4375)

A few children of function nodes need to be consistently evaluated
outside the function scope. This PR attempts to do so and thus
fixes https://github.com/cython/cython/issues/4367.

Cython/Compiler/Nodes.py

@@ -1750,6 +1750,8 @@ class FuncDefNode(StatNode, BlockNode):
     code_object = None
     return_type_annotation = None
 
+    outer_attrs = None  # overridden by some derived classes - to be visited outside the node's scope
+
     def analyse_default_values(self, env):
         default_seen = 0
         for arg in self.args:

Cython/Compiler/ParseTreeTransforms.py

@@ -2054,8 +2054,6 @@ if VALUE is not None:
     def visit_DefNode(self, node):
         node = self.visit_FuncDefNode(node)
         env = self.current_env()
-        if isinstance(node, Nodes.DefNode) and node.is_wrapper:
-            env = env.parent_scope
         if (not isinstance(node, Nodes.DefNode) or
                 node.fused_py_func or node.is_generator_body or
                 not node.needs_assignment_synthesis(env)):

Cython/Compiler/Visitor.py

@@ -370,8 +370,10 @@ class EnvTransform(CythonTransform):
         self.env_stack.pop()
 
     def visit_FuncDefNode(self, node):
+        outer_attrs = node.outer_attrs
+        self.visitchildren(node, attrs=outer_attrs)
         self.enter_scope(node, node.local_scope)
-        self._process_children(node)
+        self.visitchildren(node, attrs=None, exclude=outer_attrs)
         self.exit_scope()
         return node
 

tests/run/decorators.pyx

@@ -61,3 +61,23 @@ a = A()
 @a.decorate
 def i(x):
     return x - 1
+
+def append_to_list_decorator(lst):
+    def do_append_to_list_dec(func):
+        def new_func():
+            return lst + func()
+        return new_func
+    return do_append_to_list_dec
+
+def outer(arg1, arg2):
+    """
+    ensure decorators are analysed in the correct scope
+    https://github.com/cython/cython/issues/4367
+    mainly intended as a compile-time test (but it does run...)
+    >>> outer(append_to_list_decorator, [1,2,3])
+    [1, 2, 3, 4]
+    """
+    @arg1([x for x in arg2])
+    def method():
+        return [4]
+    return method()