gh-99341: Cover type ignore nodes when incrementing line numbers (GH-99422)

(cherry picked from commit 1acdfec)

Co-authored-by: Batuhan Taskaya <isidentical@gmail.com>

Author: miss-islington

Lib/ast.py

@@ -236,6 +236,12 @@ def increment_lineno(node, n=1):
     location in a file.
     """
     for child in walk(node):
+        # TypeIgnore is a special case where lineno is not an attribute
+        # but rather a field of the node itself.
+        if isinstance(child, TypeIgnore):
+            child.lineno = getattr(child, 'lineno', 0) + n
+            continue
+
         if 'lineno' in child._attributes:
             child.lineno = getattr(child, 'lineno', 0) + n
         if (

Lib/test/test_ast.py

@@ -1026,6 +1026,18 @@ def test_increment_lineno(self):
         self.assertEqual(ast.increment_lineno(src).lineno, 2)
         self.assertIsNone(ast.increment_lineno(src).end_lineno)
 
+    def test_increment_lineno_on_module(self):
+        src = ast.parse(dedent("""\
+        a = 1
+        b = 2 # type: ignore
+        c = 3
+        d = 4 # type: ignore@tag
+        """), type_comments=True)
+        ast.increment_lineno(src, n=5)
+        self.assertEqual(src.type_ignores[0].lineno, 7)
+        self.assertEqual(src.type_ignores[1].lineno, 9)
+        self.assertEqual(src.type_ignores[1].tag, '@tag')
+
     def test_iter_fields(self):
         node = ast.parse('foo()', mode='eval')
         d = dict(ast.iter_fields(node.body))

Misc/NEWS.d/next/Library/2022-11-13-02-06-56.gh-issue-99341.8-OlwB.rst

@@ -0,0 +1,2 @@
+Fix :func:`ast.increment_lineno` to also cover :class:`ast.TypeIgnore` when
+changing line numbers.