Bypass class attribute lookup for PEP 695 typevars

Author: A5rocks

mypy/semanal.py

@@ -1842,24 +1842,26 @@ def push_type_args(
                 return None
             tvs.append((p.name, tv))
 
-            if self.is_defined_type_param(p.name):
+            if old_tv := self.is_defined_type_param(p.name):
                 self.fail(f'"{p.name}" already defined as a type parameter', context)
+                # we rely on the typevar being at self.locals[-1] later, so this needs to happen
+                self.add_symbol(p.name, old_tv, context, no_progress=True, type_param=True)
             else:
                 assert self.add_symbol(
                     p.name, tv, context, no_progress=True, type_param=True
                 ), "Type parameter should not be discarded"
 
         return tvs
 
-    def is_defined_type_param(self, name: str) -> bool:
+    def is_defined_type_param(self, name: str) -> TypeVarLikeExpr | None:
         for names in self.locals:
             if names is None:
                 continue
             if name in names:
                 node = names[name].node
                 if isinstance(node, TypeVarLikeExpr):
-                    return True
-        return False
+                    return node
+        return None
 
     def analyze_type_param(
         self, type_param: TypeParam, context: Context
@@ -2272,7 +2274,8 @@ class Foo(Bar, Generic[T]): ...
         has_type_var_tuple = False
         if defn.type_args is not None:
             for p in defn.type_args:
-                node = self.lookup(p.name, context)
+                assert self.locals[-1], "expected PEP 695 type vars in locals"
+                node = self.locals[-1][p.name]
                 assert node is not None
                 assert isinstance(node.node, TypeVarLikeExpr)
                 if isinstance(node.node, TypeVarTupleExpr):

test-data/unit/check-python312.test

@@ -2237,3 +2237,10 @@ class D[*Ts](Generic[Unpack[Us]]):  # E: Generic[...] base class is redundant \
                                     # E: Can only use one type var tuple in a class def
     pass
 [builtins fixtures/tuple.pyi]
+
+[case testPEP695TypeVarReusedName]
+class C:
+    X = 5
+    class Inner[X]:
+        pass
+[builtins fixtures/tuple.pyi]