False-positive type errors when passing **kwargs to a function that has other keyword args

Bug Report

If a function signature contains one or more explicit keyword parameters followed by a **kwargs parameter, and the function is called on kwargs only, then mypy generates false positive type errors.

The number of errors generated is unbounded and appears to be equal to the number of distinct types found among the explicit keyword parameters. In addition, the errors are mutually inconsistent with one another (see example below).

To Reproduce

from typing import Any, Optional

def example(
	*,
	a: Optional[int] = None,
	b: Optional[float] = None,
	c: Optional[bool] = None,
	d: Optional[list] = None,
	**kwargs
) -> None:
	print(kwargs)

kwargs = {'hello': 'world'}
example(**kwargs)

Expected Behavior

I'd expect this to pass type-checking: it looks perfectly correct to me. All I'm doing is passing kwargs into kwargs.

Actual Behavior

example.py:14: error: Argument 1 to "example" has incompatible type "**dict[str, str]"; expected "Optional[int]"  [arg-type]
example.py:14: error: Argument 1 to "example" has incompatible type "**dict[str, str]"; expected "Optional[float]"  [arg-type]
example.py:14: error: Argument 1 to "example" has incompatible type "**dict[str, str]"; expected "Optional[bool]"  [arg-type]
example.py:14: error: Argument 1 to "example" has incompatible type "**dict[str, str]"; expected "Optional[list[Any]]"  [arg-type]
Found 4 errors in 1 file (checked 1 source file)

In addition to being false positives, these errors are mutually inconsistent: mypy is claiming that an Optional[int] is expected in Argument 1, and also that an Optional[float] is expected in Argument 1, and also that an Optional[bool] is expected in Argument 1, and so on!

If I change the last line to this:

example(a=None, b=None, c=None, d=None, **kwargs)

then the errors go away. Is this really what mypy wants me to do??

Your Environment

• Mypy version used: 1.14.1
• Mypy command-line flags: None
• Mypy configuration options from pyproject.toml:

allow_redefinition = true
disable_error_code = "no-any-unimported, no-any-return"
disallow_any_unimported = true
check_untyped_defs = true
follow_imports = "silent"
plugins = "pydantic.mypy"
show_error_codes = true
strict_optional = false
warn_return_any = true
warn_unused_ignores = true

• Python version used: 3.9.20

まず、mypy 1.14.1 で issue の例を再現し、**kwargs に続く明示的なキーワードパラメーターに対するキーワード引数のチェック経路を追跡します。示されている呼び出しの回帰テストを追加し、誤検出のエラーが発生しないことを確認するとともに、互換性のない明示的なキーワードを含む呼び出しは引き続きチェックされることを確認します。