Corrected the parent of function type comment nodes

These nodes used to be parented to their original ast.FunctionDef parent
but are now correctly parented to their astroid.FunctionDef parent.

Closes #851

Author: AWhetter

ChangeLog

@@ -119,6 +119,13 @@ Release Date: TBA
 
   Close PyCQA/pylint#3904
 
+* Corrected the parent of function type comment nodes.
+
+  These nodes used to be parented to their original ast.FunctionDef parent
+  but are now correctly parented to their astroid.FunctionDef parent.
+
+  Close PyCQA/astroid#851
+
 
 What's New in astroid 2.4.2?
 ============================

astroid/rebuilder.py

@@ -238,7 +238,7 @@ def check_type_comment(self, node, parent):
 
         return type_object.value
 
-    def check_function_type_comment(self, node):
+    def check_function_type_comment(self, node, parent):
         type_comment = getattr(node, "type_comment", None)
         if not type_comment:
             return None
@@ -251,10 +251,10 @@ def check_function_type_comment(self, node):
 
         returns = None
         argtypes = [
-            self.visit(elem, node) for elem in (type_comment_ast.argtypes or [])
+            self.visit(elem, parent) for elem in (type_comment_ast.argtypes or [])
         ]
         if type_comment_ast.returns:
-            returns = self.visit(type_comment_ast.returns, node)
+            returns = self.visit(type_comment_ast.returns, parent)
 
         return returns, argtypes
 
@@ -615,7 +615,7 @@ def _visit_functiondef(self, cls, node, parent):
             returns = None
 
         type_comment_args = type_comment_returns = None
-        type_comment_annotation = self.check_function_type_comment(node)
+        type_comment_annotation = self.check_function_type_comment(node, newnode)
         if type_comment_annotation:
             type_comment_returns, type_comment_args = type_comment_annotation
         newnode.postinit(

tests/unittest_builder.py

@@ -544,6 +544,17 @@ def test_not_implemented(self):
         self.assertIsInstance(inferred, nodes.Const)
         self.assertEqual(inferred.value, NotImplemented)
 
+    def test_correct_function_type_comment_parent(self):
+        data = """
+            def f(a):
+                # type: (A) -> A
+                pass
+        """
+        astroid = builder.parse(data)
+        f = astroid.body[0]
+        self.assertIs(f.type_comment_args[0].parent, f)
+        self.assertIs(f.type_comment_returns.parent, f)
+
 
 class FileBuildTest(unittest.TestCase):
     def setUp(self):