I am having trouble getting the numpy.typing.mypy_plugin to work.
Following the example of how to use NBitBase, I get different output from mypy.

Problem

expected behavior

According to the docs, the output should be:

    # note: Revealed local types are:
    # note:     a: numpy.floating[numpy.typing._16Bit*]
    # note:     b: numpy.signedinteger[numpy.typing._64Bit*]
    # note:     out: numpy.floating[numpy.typing._64Bit*]

actual behavior

My output, from running mypy on the example code is:

╭sam@sam-XPS-15-7590:2 ...mpy_mypy_plugin_not_working ❖ do 16 10:19 
╰[poetry: numpy_mypy_plugin_not_working/.venv]$ mypy
src/example/__init__.py:22: note: Revealed local types are:
src/example/__init__.py:22: note:     a: numpy.floating[numpy._typing._16Bit]
src/example/__init__.py:22: note:     b: numpy.signedinteger[numpy._typing._64Bit]
src/example/__init__.py:22: note:     out: numpy.floating[Union[numpy._typing._16Bit, numpy._typing._64Bit]]

MWE

Below is MWE to reproduce the error.
I attached the poetry lock file in a gist here.

src/example/__init__.py

from typing import TYPE_CHECKING, TypeVar

import numpy as np
import numpy.typing as npt

T1 = TypeVar("T1", bound=npt.NBitBase)
T2 = TypeVar("T2", bound=npt.NBitBase)


def add(a: np.floating[T1], b: np.integer[T2]) -> np.floating[T1 | T2]:
    return a + b


a = np.float16()
b = np.int64()
out = add(a, b)
print(a)
print(b)
print(out)

if TYPE_CHECKING:
    reveal_locals()

pyproject.toml

[tool.poetry]
name = "example"
version = "0.1.0"
description = "Foo"
authors = ["Sam De Meyer <[email protected]>"]
packages = [{ include = "example", from = "src" }]


[tool.poetry.dependencies]
python = ">=3.11,<=3.12"
numpy = "^1.26.4"

[tool.poetry.group.dev.dependencies]
mypy = "^1.8.0"

[build-system]
requires = ["poetry-core>=1.7"]
build-backend = "poetry.core.masonry.api"

[tool.mypy]
files = ["src/example"]
python_version = "3.11"
pretty = true
plugins = ["numpy.typing.mypy_plugin"]

To recreate the python venv, put the above files under the same directory as:

.
├── pyproject.toml
└── src
    └── example
        └── __init__.py

Then run poetry install to create a venv with the same package versions.

What I tried

• I verified that I was using the correct python and mypy executables:

  ╭sam@sam-XPS-15-7590:2 ...mpy_mypy_plugin_not_working ❖ do 16 10:50 ✘1 
  ╰[poetry: numpy_mypy_plugin_not_working/.venv]$ poetry show
  mypy              1.10.0 Optional static typing for Python
  mypy-extensions   1.0.0  Type system extensions for programs checked with the mypy type checker.
  numpy             1.26.4 Fundamental package for array computing in Python
  typing-extensions 4.11.0 Backported and Experimental Type Hints for Python 3.8+
  ╭sam@sam-XPS-15-7590:2 ...mpy_mypy_plugin_not_working ❖ do 16 10:51 
  ╰[poetry: numpy_mypy_plugin_not_working/.venv]$ which python
  /home/sam/Safe/Proj/Scratch/numpy_mypy_plugin_not_working/.venv/bin/python
  ╭sam@sam-XPS-15-7590:2 ...mpy_mypy_plugin_not_working ❖ do 16 10:52 
  ╰[poetry: numpy_mypy_plugin_not_working/.venv]$ which mypy
  /home/sam/Safe/Proj/Scratch/numpy_mypy_plugin_not_working/.venv/bin/mypy
  

• I verified that mypy is picking up the plugin settings. If I make a typo in the plugin name I get:

  ╭sam@sam-XPS-15-7590:2 ...mpy_mypy_plugin_not_working ❖ do 16 10:22 
  ╰[poetry: numpy_mypy_plugin_not_working/.venv]$ mypy
  pyproject.toml:1: error: Error importing plugin "numpy.typing.mypy_plugi": No module named 'numpy.typing.mypy_plugi'  [misc]
      [tool.poetry]
      ^
  Found 1 error in 1 file (errors prevented further checking)
  

  Which I see as sufficient proof that mypy is loading the plugin if typed correctly.

• I tried disabling (commenting out) the line:

  plugins = ["numpy.typing.mypy_plugin"]
  

  Which resulted in the exact same (wrong) output of mypy