Permit subscripting additional builtin classes (#1572)

Treat other classes such as enumerate and staticmethod identically to list, dict, tuple, set, frozenset.

Author: jacobtylerwalls

ChangeLog

@@ -26,6 +26,9 @@ Release date: TBA
 
   Closes #1559
 
+* On Python versions >= 3.9, ``astroid`` now understands subscripting
+  builtin classes such as ``enumerate`` or ``staticmethod``.
+
 * Rename ``ModuleSpec`` -> ``module_type`` constructor parameter to match attribute
   name and improve typing. Use ``type`` instead.
 

astroid/nodes/scoped_nodes/scoped_nodes.py

@@ -2763,7 +2763,7 @@ def getitem(self, index, context=None):
             # AttributeError
             if (
                 isinstance(method, node_classes.EmptyNode)
-                and self.name in {"list", "dict", "set", "tuple", "frozenset"}
+                and self.pytype() == "builtins.type"
                 and PY39_PLUS
             ):
                 return self

tests/unittest_brain.py

@@ -1271,10 +1271,9 @@ def test_invalid_type_subscript(self):
 
     @test_utils.require_version(minver="3.9")
     def test_builtin_subscriptable(self):
-        """
-        Starting with python3.9 builtin type such as list are subscriptable
-        """
-        for typename in ("tuple", "list", "dict", "set", "frozenset"):
+        """Starting with python3.9 builtin types such as list are subscriptable.
+        Any builtin class such as "enumerate" or "staticmethod" also works."""
+        for typename in ("tuple", "list", "dict", "set", "frozenset", "enumerate"):
             src = f"""
             {typename:s}[int]
             """

tests/unittest_inference.py

@@ -3574,7 +3574,6 @@ def test_invalid_slicing_primaries(self) -> None:
             "(1, 2, 3)[a:]",
             "(1, 2, 3)[object:object]",
             "(1, 2, 3)[1:object]",
-            "enumerate[2]",
         ]
         for code in examples:
             node = extract_node(code)