microsoft / microsoft/pyright

Generic method argument with Self type causes incomplete signature

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bug
Dominant language
Python
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Description

Describe the bug
pyright seems to mis-infer the signature of a method when an parameter to a generic argument is a self-type that is checked against a protocol.

Code or Screenshots

from __future__ import annotations

from typing import Any, Protocol, Self

class _ViewP(Protocol):
    # XXX: Any should really be some sort of `Pipeline`-bound TypeVar...
    def dispatch(self, pipeline: Any) -> None:
        ...

class PipelineView:
    def dispatch(self, pipeline: Pipeline[Self]) -> None:
        ...

class Pipeline[ViewT: _ViewP]:
    def pipeline_views(self) -> ViewT:
        ...

This produces

repro.py:11:43 - error: Type "Self@PipelineView" cannot be assigned to type variable "ViewT@Pipeline"
    Type "PipelineView*" is not assignable to upper bound "_ViewP" for type variable "ViewT@Pipeline"
      "PipelineView*" is incompatible with protocol "_ViewP"
        "dispatch" is an incompatible type
          Type "() -> Unknown" is not assignable to type "(pipeline: Any) -> None"
            Function accepts too many positional parameters; expected 0 but received 1 (reportInvalidTypeArguments)
1 error, 0 warnings, 0 informations

VS Code extension or command-line
Using pyright 1.1.402 through the CLI.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the repro.py example and run it through the CLI using pyright 1.1.402 to reproduce the Self and protocol diagnostic. Trace the type-checking path for the generic Pipeline[Self] argument, then verify that the example no longer reports the incompatible dispatch signature.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
45/100

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