Changes after review

astroid/brain/brain_typing.py

@@ -169,7 +169,7 @@ def infer_typing_attr(
             # node.parent.slots is evaluated and cached before the inference tip
             # is first applied. Remove the last result to allow a recalculation of slots
             cache = getattr(node.parent, "__cache")
-            if cache and cache.get(node.parent.slots) is not None:
+            if cache.get(node.parent.slots) is not None:
                 del cache[node.parent.slots]
         return iter([value])
 

astroid/scoped_nodes.py

@@ -104,36 +104,39 @@ def _c3_merge(sequences, cls, context):
 
 
 def clean_typing_generic_mro(sequences: List[List["ClassDef"]]) -> None:
-    """typing.Generic is allowed to appear multiple times in the initial mro.
-    The final one however, MUST only contain ONE.
+    """A class can inherit from typing.Generic directly, as base,
+    and as base of bases. The merged MRO must however, only contain the last entry.
+    To prepare for _c3_merge, remove some typing.Generic entries from
+    sequences if multiple are present.
 
-    This method will check if Generic is in inferred_bases, but also
+    This method will check if Generic is in inferred_bases and also
     part of bases_mro. If true, remove it from inferred_bases
     as well as its entry the bases_mro.
 
     Format sequences: [[self]] + bases_mro + [inferred_bases]
     """
-    pos_generic_in_main_bases = -1
-    # Check if part of inferred_bases
-    for i, base in enumerate(sequences[-1]):
+    bases_mro = sequences[1:-1]
+    inferred_bases = sequences[-1]
+    # Check if Generic is part of inferred_bases
+    for i, base in enumerate(inferred_bases):
         if base.qname() == "typing.Generic":
-            pos_generic_in_main_bases = i
+            position_in_inferred_bases = i
             break
     else:
         return
     # Check if also part of bases_mro
     # Ignore entry for typing.Generic
-    for i, seq in enumerate(sequences[1:-1]):
-        if i == pos_generic_in_main_bases:
+    for i, seq in enumerate(bases_mro):
+        if i == position_in_inferred_bases:
             continue
         if any(base.qname() == "typing.Generic" for base in seq):
             break
     else:
         return
     # Found multiple Generics in mro, remove entry from inferred_bases
     # and the corresponding one from bases_mro
-    sequences[-1].pop(pos_generic_in_main_bases)
-    sequences.pop(pos_generic_in_main_bases + 1)
+    inferred_bases.pop(position_in_inferred_bases)
+    bases_mro.pop(position_in_inferred_bases)
 
 
 def clean_duplicates_mro(sequences, cls, context):