Avoid duplicate inference results for Tuple[Optional[int], ...] (#2340)

Author: jacobtylerwalls

ChangeLog

@@ -17,6 +17,11 @@ What's New in astroid 3.0.2?
 ============================
 Release date: TBA
 
+* Avoid duplicate inference results for some uses of ``typing.X`` constructs like
+  ``Tuple[Optional[int], ...]``. This was causing pylint to occasionally omit
+  messages like ``deprecated-typing-alias``.
+
+  Closes pylint-dev/pylint#9220
 
 
 What's New in astroid 3.0.1?

astroid/brain/brain_typing.py

@@ -188,6 +188,8 @@ def infer_typing_attr(
             cache = node.parent.__cache  # type: ignore[attr-defined] # Unrecognized getattr
             if cache.get(node.parent.slots) is not None:
                 del cache[node.parent.slots]
+        # Avoid re-instantiating this class every time it's seen
+        node._explicit_inference = lambda node, context: iter([value])
         return iter([value])
 
     node = extract_node(TYPING_TYPE_TEMPLATE.format(value.qname().split(".")[-1]))
@@ -393,6 +395,8 @@ def infer_special_alias(
     class_def.postinit(bases=[res], body=[], decorators=None)
     func_to_add = _extract_single_node(CLASS_GETITEM_TEMPLATE)
     class_def.locals["__class_getitem__"] = [func_to_add]
+    # Avoid re-instantiating this class every time it's seen
+    node._explicit_inference = lambda node, context: iter([class_def])
     return iter([class_def])
 
 

tests/brain/test_brain.py

@@ -668,6 +668,16 @@ def test_typing_no_duplicates(self):
         )
         assert len(node.inferred()) == 1
 
+    @test_utils.require_version(minver="3.9")
+    def test_typing_no_duplicates_2(self):
+        node = builder.extract_node(
+            """
+        from typing import Optional, Tuple
+        Tuple[Optional[int], ...]
+        """
+        )
+        assert len(node.inferred()) == 1
+
     def test_collections_generic_alias_slots(self):
         """Test slots for a class which is a subclass of a generic alias type."""
         node = builder.extract_node(