Fixed handling of *args in the functools overlay

See added test for an example where pytype previously crashed.

PiperOrigin-RevId: 831282244

Author: superbobry

pytype/overlays/functools_overlay.py

@@ -49,14 +49,18 @@ def __init__(self, ctx: "context.Context", module: str):
   def new_slot(
       self, node, cls, func, /, *args, **kwargs
   ) -> tuple[cfg.CFGNode, cfg.Variable]:
+    # We are not using ``cls``, because it is set to unsolvable when
+    # functools.partial is called with *args.
+    del cls
+
     # Make sure the call is well typed before binding the partial
     new = self.ctx.convert.convert_pytd_function(self._pytd_new)
     _, specialized_obj = function.call_function(
         self.ctx,
         node,
         new.to_variable(node),
         function.Args(
-            (cls, func, *args),
+            (self.to_variable(node), func, *args),
             kwargs,
             call_context.starargs,
             call_context.starstarargs,
@@ -65,8 +69,7 @@ def new_slot(
     )
     [specialized_obj] = specialized_obj.data
     type_arg = specialized_obj.get_formal_type_parameter("_T")
-    [cls] = cls.data
-    cls = abstract.ParameterizedClass(cls, {"_T": type_arg}, self.ctx)
+    cls = abstract.ParameterizedClass(self, {"_T": type_arg}, self.ctx)
     obj = bind_partial(node, cls, func, args, kwargs, self.ctx)
     return node, obj.to_variable(node)
 

pytype/tests/test_functions1.py

@@ -1070,6 +1070,20 @@ def f(a, b) -> None: ...
     """,
     )
 
+  def test_functools_partial_star(self):
+    self.Check("""
+      from typing import Any
+      import functools
+      def f() -> int :
+        return 42
+      def test(*args):
+        assert_type(functools.partial(*args), functools.partial[Any])
+
+        # This is WAI in pytype, since *args currently overwrite *all* other
+        # arguments, including the ones bound positionally prior to *args.
+        assert_type(functools.partial(f, *args), functools.partial[Any])
+    """)
+
   def test_functools_partial_kw(self):
     self.Check("""
       import functools