Crash when **unpacking kwargs typed with a TypedDict into a function typed with ParamSpec in expand_actual_type

[jmahlik]

Crash Report
This originally occurred when trying to type hint keyword args to a concurrent.Futures.ThreadPoolExecutor.submit. I was able to get it down to a more minimal reproducer. Seems that any kwargs **unpacking where the kwargs are a typed dict can trigger it.

Traceback

mypy ./typed_dict_crash.py --show-traceback

typed_dict_crash.py:37: 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: 1.8.0+dev.7c33e7c03444ae748b82163e7b4e1666dfaf94c7
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File ".venv\Scripts\mypy.exe\__main__.py", line 7, in <module>
    sys.exit(console_entry())
  File ".venv\Lib\site-packages\mypy\__main__.py", line 15, in console_entry
    main()
  File ".venv\Lib\site-packages\mypy\main.py", line 100, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File ".venv\Lib\site-packages\mypy\main.py", line 182, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File ".venv\Lib\site-packages\mypy\build.py", line 191, in build
    result = _build(
  File ".venv\Lib\site-packages\mypy\build.py", line 265, in _build
    graph = dispatch(sources, manager, stdout)
  File ".venv\Lib\site-packages\mypy\build.py", line 2943, in dispatch
    process_graph(graph, manager)
  File ".venv\Lib\site-packages\mypy\build.py", line 3341, in process_graph
    process_stale_scc(graph, scc, manager)
  File ".venv\Lib\site-packages\mypy\build.py", line 3442, in process_stale_scc
    graph[id].type_check_first_pass()
  File ".venv\Lib\site-packages\mypy\build.py", line 2311, in type_check_first_pass
    self.type_checker().check_first_pass()
  File ".venv\Lib\site-packages\mypy\checker.py", line 481, in check_first_pass
    self.accept(d)
  File ".venv\Lib\site-packages\mypy\checker.py", line 591, in accept
    stmt.accept(self)
  File ".venv\Lib\site-packages\mypy\nodes.py", line 787, in accept
    return visitor.visit_func_def(self)
  File ".venv\Lib\site-packages\mypy\checker.py", line 1000, in visit_func_def
    self._visit_func_def(defn)
  File ".venv\Lib\site-packages\mypy\checker.py", line 1004, in _visit_func_def
    self.check_func_item(defn, name=defn.name)
  File ".venv\Lib\site-packages\mypy\checker.py", line 1077, in check_func_item
    self.check_func_def(defn, typ, name, allow_empty)
  File ".venv\Lib\site-packages\mypy\checker.py", line 1293, in check_func_def
    self.accept(item.body)
  File ".venv\Lib\site-packages\mypy\checker.py", line 591, in accept
    stmt.accept(self)
  File ".venv\Lib\site-packages\mypy\nodes.py", line 1223, in accept
    return visitor.visit_block(self)
  File ".venv\Lib\site-packages\mypy\checker.py", line 2770, in visit_block
    self.accept(s)
  File ".venv\Lib\site-packages\mypy\checker.py", line 591, in accept
    stmt.accept(self)
  File ".venv\Lib\site-packages\mypy\nodes.py", line 1310, in accept
    return visitor.visit_assignment_stmt(self)
  File ".venv\Lib\site-packages\mypy\checker.py", line 2818, in visit_assignment_stmt
    self.check_assignment(s.lvalues[-1], s.rvalue, s.type is None, s.new_syntax)
  File ".venv\Lib\site-packages\mypy\checker.py", line 3026, in check_assignment
    rvalue_type = self.expr_checker.accept(rvalue, type_context=type_context)
  File ".venv\Lib\site-packages\mypy\checkexpr.py", line 5727, in accept
    typ = node.accept(self)
          ^^^^^^^^^^^^^^^^^
  File ".venv\Lib\site-packages\mypy\nodes.py", line 1904, in accept
    return visitor.visit_call_expr(self)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv\Lib\site-packages\mypy\checkexpr.py", line 473, in visit_call_expr
    return self.visit_call_expr_inner(e, allow_none_return=allow_none_return)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv\Lib\site-packages\mypy\checkexpr.py", line 602, in visit_call_expr_inner
    ret_type = self.check_call_expr_with_callee_type(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv\Lib\site-packages\mypy\checkexpr.py", line 1440, in check_call_expr_with_callee_type
    ret_type, callee_type = self.check_call(
                            ^^^^^^^^^^^^^^^^
  File ".venv\Lib\site-packages\mypy\checkexpr.py", line 1535, in check_call
    return self.check_callable_call(
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv\Lib\site-packages\mypy\checkexpr.py", line 1720, in check_callable_call
    callee = self.infer_function_type_arguments(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv\Lib\site-packages\mypy\checkexpr.py", line 2045, in infer_function_type_arguments
    inferred_args, _ = infer_function_type_arguments(
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv\Lib\site-packages\mypy\infer.py", line 56, in infer_function_type_arguments
    constraints = infer_constraints_for_callable(
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv\Lib\site-packages\mypy\constraints.py", line 226, in infer_constraints_for_callable
    actual_type = mapper.expand_actual_type(
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv\Lib\site-packages\mypy\argmap.py", line 248, in expand_actual_type
    formal_name = (set(actual_type.items.keys()) - self.kwargs_used).pop()
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
KeyError: 'pop from an empty set'
typed_dict_crash.py:37: : note: use --pdb to drop into pdb

To Reproduce

from typing import Callable, ParamSpec, TypedDict, TypeVar

_T = TypeVar("_T")
_P = ParamSpec("_P")


def submit(__fn: Callable[_P, _T], *args: _P.args, **kwargs: _P.kwargs) -> _T:
    """Similar to concurrent.futures.ThreadPoolExecutor.submit.

    https://github.com/python/typeshed/blob/0f7241844eb2692fca8b43994f0e238c50d48d46/stdlib/concurrent/futures/_base.pyi#L51

    Minimal stub to repro.
    """
    return __fn(*args, **kwargs)


def f(one: str | None = None, **kwargs: str) -> str | None:
    print(kwargs)
    return one


class D(TypedDict):
    """Keyword args to f."""

    one: str
    two: str


def func(
    typed_dict: D,
) -> None | str:
    """Pass kwargs to an underlying function via a typed dict."""
    # Originally this was a concurrent.futures.ThreadPoolExecutor.submit
    result = submit(f, **typed_dict)
    print(result)

    return result


# Both cases will crash
d = D(one="hello", two="world")
submit(f, **d)

func({"one": "hello", "two": "world"})

Your Environment

• Mypy version used: 1.7.1 and current main at 7c33e7c03444ae748b82163e7b4e1666dfaf94c7
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.12, 3.11
• Operating system and version: Windows 10

[hauntsaninja]

Someone at work just ran into this, here's the repro I minimised from that:

from typing import *

P = ParamSpec("P")
R = TypeVar("R")

def run(func: Callable[P, R], *args: P.args, **kwargs: P.kwargs) -> R: ...

class Params(TypedDict):
    temperature: float

class BRTC:
    def complete(self, c: Callable[..., None], **params: Unpack[Params]) -> None:
        run(c, **params)