Fix regression on Compare node inference (#1185)

This deals with pylint-dev/pylint#5048

ChangeLog

@@ -22,6 +22,10 @@ Release date: TBA
   Closes PyCQA/pylint#5030
   Closes PyCQA/pylint#5036
 
+* Fix regression on Compare node inference
+
+  Closes PyCQA/pylint#5048
+
 
 What's New in astroid 2.8.0?
 ============================

astroid/inference.py

@@ -810,6 +810,7 @@ def infer_binop(self, context=None):
 
 def _to_literal(node: nodes.NodeNG) -> Any:
     # Can raise SyntaxError or ValueError from ast.literal_eval
+    # Can raise AttributeError from node.as_string() as not all nodes have a visitor
     # Is this the stupidest idea or the simplest idea?
     return ast.literal_eval(node.as_string())
 
@@ -840,7 +841,7 @@ def _do_compare(
 
         try:
             left, right = _to_literal(left), _to_literal(right)
-        except (SyntaxError, ValueError):
+        except (SyntaxError, ValueError, AttributeError):
             return util.Uninferable
 
         try:

tests/unittest_inference.py

@@ -5527,6 +5527,18 @@ def func(a, b):
     assert inferred[0] is util.Uninferable
 
 
+def test_compare_unknown() -> None:
+    code = """
+    def func(a):
+        if tuple() + (a[1],) in set():
+            raise Exception()
+    """
+    node = extract_node(code)
+    inferred = list(node.infer())
+    assert len(inferred) == 1
+    assert isinstance(inferred[0], nodes.FunctionDef)
+
+
 def test_limit_inference_result_amount() -> None:
     """Test setting limit inference result amount"""
     code = """