Use nodes.Unknown instead of Uninferable for specifying unknown inference results

In the context of binop inference for lists and tuples, we were rebuilding
a collection with the inferred elements. We were using Uninferable for specifying inference failures, but this leads to having non-AST nodes in collection's elts attribute, which should not happen. Instead, we replaced Uninferable with Unknown, meaning now we have an AST object.

1 files changed, 5 insertions, 2 deletions

diff --git a/astroid/protocols.py b/astroid/protocols.py
index d1abdea0..605ae1ce 100644
--- a/astroid/protocols.py
+++ b/astroid/protocols.py
@@ -147,10 +147,13 @@ def _multiply_seq_by_int(self, opnode, other, context):
 def _filter_uninferable_nodes(elts, context):
     for elt in elts:
         if elt is util.Uninferable:
-            yield elt
+            yield nodes.Unknown()
         else:
             for inferred in elt.infer(context):
-                yield inferred
+                if inferred is not util.Uninferable:
+                    yield inferred
+                else:
+                    yield nodes.Unknown()
 
 
 @decorators.yes_if_nothing_inferred