fix Odd warning on shutil.rmtree and ExitStack.callback #2105

[asukaminato0721]

Summary

Fixes #2105

Fixed ParamSpec inference for forwarded callbacks to select the overload that matches the forwarded arguments, even when the callback is a bound __call__ (protocol/class instance).

Test Plan

Added a regression test for ExitStack.callback(shutil.rmtree, ..., ignore_errors=True).

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

pwndbg (https://github.com/pwndbg/pwndbg)
- ERROR pwndbg/dbg_mod/lldb/repl/fuzzy.py:127:20-45: Missing argument `ignore_errors` in function `atexit.register` [missing-argument]
- ERROR pwndbg/dbg_mod/lldb/repl/fuzzy.py:127:20-45: Missing argument `onerror` in function `atexit.register` [missing-argument]
- ::error file=pwndbg/dbg_mod/lldb/repl/fuzzy.py,line=127,col=20,endLine=127,endColumn=45,title=Pyrefly missing-argument::Missing argument `ignore_errors` in function `atexit.register`
- ::error file=pwndbg/dbg_mod/lldb/repl/fuzzy.py,line=127,col=20,endLine=127,endColumn=45,title=Pyrefly missing-argument::Missing argument `onerror` in function `atexit.register`

tornado (https://github.com/tornadoweb/tornado)
+ ERROR tornado/gen.py:255:62-69: Argument `Awaitable[Unknown] | Future[Unknown] | dict[Any, Awaitable[Unknown]] | list[Awaitable[Unknown]] | _T | None` is not assignable to parameter `first_yielded` with type `Awaitable[Unknown] | Future[Unknown] | dict[Any, Awaitable[Unknown]] | list[Awaitable[Unknown]] | None` in function `Runner.__init__` [bad-argument-type]
+ ::error file=tornado/gen.py,line=255,col=62,endLine=255,endColumn=69,title=Pyrefly bad-argument-type::Argument `Awaitable[Unknown] | Future[Unknown] | dict[Any, Awaitable[Unknown]] | list[Awaitable[Unknown]] | _T | None` is not assignable to parameter `first_yielded` with type `Awaitable[Unknown] | Future[Unknown] | dict[Any, Awaitable[Unknown]] | list[Awaitable[Unknown]] | None` in function `Runner.__init__`

starlette (https://github.com/encode/starlette)
+ ERROR starlette/testclient.py:112:28-39: Argument `BoundMethod[BlockingPortal, Overload[
+   [PosArgsT, T_Retval](self: BlockingPortal, func: (**tuple[*PosArgsT]) -> Awaitable[T_Retval], *args: *PosArgsT) -> T_Retval
+   [PosArgsT, T_Retval](self: BlockingPortal, func: (**tuple[*PosArgsT]) -> T_Retval, *args: *PosArgsT) -> T_Retval
+ ]]` is not assignable to parameter with type `(func: (**tuple[*PosArgsT]) -> Awaitable[T_Retval], *args: *PosArgsT) -> @_` in function `contextlib._BaseExitStack.callback` [bad-argument-type]
+ ::error file=starlette/testclient.py,line=112,col=28,endLine=112,endColumn=39,title=Pyrefly bad-argument-type::Argument `BoundMethod[BlockingPortal, Overload[%0A  [PosArgsT, T_Retval](self: BlockingPortal, func: (**tuple[*PosArgsT]) -> Awaitable[T_Retval], *args: *PosArgsT) -> T_Retval%0A  [PosArgsT, T_Retval](self: BlockingPortal, func: (**tuple[*PosArgsT]) -> T_Retval, *args: *PosArgsT) -> T_Retval%0A]]` is not assignable to parameter with type `(func: (**tuple[*PosArgsT]) -> Awaitable[T_Retval], *args: *PosArgsT) -> @_` in function `contextlib._BaseExitStack.callback`

ibis (https://github.com/ibis-project/ibis)
- ERROR ibis/backends/clickhouse/tests/conftest.py:146:32-156:18: Missing argument `text` in function `concurrent.futures._base.Executor.submit` [missing-argument]
- ERROR ibis/backends/tests/base.py:362:25-372:18: Missing argument `text` in function `concurrent.futures._base.Executor.submit` [missing-argument]
- ::error file=ibis/backends/clickhouse/tests/conftest.py,line=146,col=32,endLine=156,endColumn=18,title=Pyrefly missing-argument::Missing argument `text` in function `concurrent.futures._base.Executor.submit`
- ::error file=ibis/backends/tests/base.py,line=362,col=25,endLine=372,endColumn=18,title=Pyrefly missing-argument::Missing argument `text` in function `concurrent.futures._base.Executor.submit`

[Copilot]

Pull request overview

Fixes pyrefly’s ParamSpec inference when forwarding arguments through callback-style helpers (e.g., ExitStack.callback), ensuring the selected callable overload matches the forwarded arguments (including for bound __call__ callables), addressing issue #2105.

Changes:

• Update ParamSpec inference in call analysis to prefer the callable overload that matches forwarded *args/**kwargs.
• Add a regression test covering ExitStack.callback(shutil.rmtree, ..., ignore_errors=True).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
pyrefly/lib/alt/callable.rs	Adds logic to select an overload for a forwarded callable to constrain the ParamSpec based on forwarded arguments.
pyrefly/lib/test/paramspec.rs	Adds a regression test reproducing the ExitStack.callback(shutil.rmtree, ..., ignore_errors=True) scenario.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Overload selection here uses a “first signature with zero call errors wins” approach by iterating sigs and breaking on the first match. This can diverge from the project’s overload call evaluation logic (see pyrefly/lib/alt/overload.rs, which applies additional disambiguation steps when multiple overloads match), and could pin the ParamSpec to the wrong parameter list when multiple signatures accept the forwarded args. Consider reusing the existing overload-selection machinery (or at least its disambiguation heuristic) to choose the same overload that a normal call would select, before constraining paramspec_var.

[Copilot]

This loop potentially calls callable_infer once per candidate signature, which re-infers forwarded_args/keywords each time. In hot paths with large overload sets this can become noticeably expensive. If possible, precompute argument types once (similar to CallWithTypes in call_overloads) and/or delegate to call_overloads to benefit from its argument-flattening and matching heuristics.