Add as_string visitor for Unknown node (#1268)

3 files changed, 13 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index f08c68d7..831fb601 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -10,6 +10,10 @@ Release date: TBA
 
 * Always treat ``__class_getitem__`` as a classmethod.
 
+* Add missing ``as_string`` visitor method for ``Unknown`` node.
+
+  Closes #1264
+
 
 What's New in astroid 2.8.6?
 ============================
diff --git a/astroid/nodes/as_string.py b/astroid/nodes/as_string.py
index 427ccc15..bc8dab1c 100644
--- a/astroid/nodes/as_string.py
+++ b/astroid/nodes/as_string.py
@@ -36,6 +36,7 @@ if TYPE_CHECKING:
         MatchSingleton,
         MatchStar,
         MatchValue,
+        Unknown,
     )
 
 # pylint: disable=unused-argument
@@ -643,6 +644,9 @@ class AsStringVisitor:
     def visit_evaluatedobject(self, node):
         return node.original.accept(self)
 
+    def visit_unknown(self, node: "Unknown") -> str:
+        return str(node)
+
 
 def _import_string(names):
     """return a list of (name, asname) formatted as a string"""
diff --git a/tests/unittest_nodes.py b/tests/unittest_nodes.py
index 7c78cd23..8c860eac 100644
--- a/tests/unittest_nodes.py
+++ b/tests/unittest_nodes.py
@@ -306,6 +306,11 @@ everything = f""" " \' \r \t \\ {{ }} {'x' + x!r:a} {["'"]!s:{a}}"""
         ast = abuilder.string_build(code)
         self.assertEqual(ast.as_string().strip(), code.strip())
 
+    @staticmethod
+    def test_as_string_unknown() -> None:
+        assert nodes.Unknown().as_string() == "Unknown.Unknown()"
+        assert nodes.Unknown(lineno=1, col_offset=0).as_string() == "Unknown.Unknown()"
+
 
 class _NodeTest(unittest.TestCase):
     """test transformation of If Node"""