Crash with functools.partial and Unpack

[cdce8p]

Crash Report
Crash first introduced with the new plugin for functools.partial in #16939.
/CC @hauntsaninja

Traceback

$ mypy test.py --show-traceback
test.py:11: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 1.11.0+dev.10f18a82b612b6127659cd64aa60c10b9cc7a904
Traceback (most recent call last):
  ...
  File ".../mypy/plugins/functools.py", line 247, in partial_call_callback
    result = ctx.api.expr_checker.check_call(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../mypy/checkexpr.py", line 1554, in check_call
    return self.check_callable_call(
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../mypy/checkexpr.py", line 1643, in check_callable_call
    callee = callee.with_unpacked_kwargs().with_normalized_var_args()
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../mypy/types.py", line 2087, in with_unpacked_kwargs
    assert isinstance(last_type, TypedDictType)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError:

To Reproduce

from typing import TypedDict, Unpack
from functools import partial

class Data(TypedDict, total=False):
    a1: int

def f(**kwargs: Unpack[Data]) -> None:
    ...

def g(**kwargs: Unpack[Data]) -> None:
    partial(f, **kwargs)()

Your Environment

• Mypy version used: 1.11.0+dev.10f18a82b612b6127659cd64aa60c10b9cc7a904 (current master)
• Python version used: 3.12

--
Changing the example slightly to add a second variable to Data results in new errors but the crash goes away.

from typing import TypedDict, Unpack
from functools import partial

class Data(TypedDict, total=False):
    a1: int
    a2: int  # <-- new

def f(**kwargs: Unpack[Data]) -> None:
    ...

def g(**kwargs: Unpack[Data]) -> None:
    partial(f, **kwargs)()

test.py:12: error: "f" gets multiple values for keyword argument "a1"  [misc]
test.py:12: error: "f" gets multiple values for keyword argument "a2"  [misc]