ENH: add type stubs from numpy-stubs

Add the type stubs and tests from numpy-stubs. Things this entails:

- Copy over the stubs (numpy/__init__.pyi and
  numpy/core/_internal.pyi)
  - The only modification made was removing `ndarray.tostring` since
    it is deprecated
- Update some setup.py files to include pyi files
- Move the tests from numpy-stubs/tests into numpy/tests
  - Skip them if mypy is not installed (planning on setting up CI in a
    future PR)
  - Add a mypy.ini; use it to configure mypy in the tests
    - It tells mypy where to find NumPy in the test env
    - It ignores internal NumPy type errors (since we only want to
      consider errors from the tests cases)
  - Some small edits were made to fix test cases that were emitting
    deprecation warnings
 - Add numpy/py.typed so that the types are picked up in an
   installed version of NumPy

1 files changed, 54 insertions, 0 deletions

diff --git a/numpy/tests/reveal/ndarray_conversion.py b/numpy/tests/reveal/ndarray_conversion.py
new file mode 100644
index 000000000..411adcf63
--- /dev/null
+++ b/numpy/tests/reveal/ndarray_conversion.py
@@ -0,0 +1,54 @@
+import numpy as np
+
+nd = np.array([[1, 2], [3, 4]])
+
+# item
+reveal_type(nd.item())  # E: Any
+reveal_type(nd.item(1))  # E: Any
+reveal_type(nd.item(0, 1))  # E: Any
+reveal_type(nd.item((0, 1)))  # E: Any
+
+# tolist
+reveal_type(nd.tolist())  # E: builtins.list[Any]
+
+# itemset does not return a value
+# tostring is pretty simple
+# tobytes is pretty simple
+# tofile does not return a value
+# dump does not return a value
+# dumps is pretty simple
+
+# astype
+reveal_type(nd.astype("float"))  # E: numpy.ndarray
+reveal_type(nd.astype(float))  # E: numpy.ndarray
+reveal_type(nd.astype(float, "K"))  # E: numpy.ndarray
+reveal_type(nd.astype(float, "K", "unsafe"))  # E: numpy.ndarray
+reveal_type(nd.astype(float, "K", "unsafe", True))  # E: numpy.ndarray
+reveal_type(nd.astype(float, "K", "unsafe", True, True))  # E: numpy.ndarray
+
+# byteswap
+reveal_type(nd.byteswap())  # E: numpy.ndarray
+reveal_type(nd.byteswap(True))  # E: numpy.ndarray
+
+# copy
+reveal_type(nd.copy())  # E: numpy.ndarray
+reveal_type(nd.copy("C"))  # E: numpy.ndarray
+
+# view
+class SubArray(np.ndarray):
+    pass
+
+
+reveal_type(nd.view())  # E: numpy.ndarray
+reveal_type(nd.view(np.int64))  # E: numpy.ndarray
+# replace `Any` with `numpy.matrix` when `matrix` will be added to stubs
+reveal_type(nd.view(np.int64, np.matrix))  # E: Any
+reveal_type(nd.view(np.int64, SubArray))  # E: SubArray
+
+# getfield
+reveal_type(nd.getfield("float"))  # E: numpy.ndarray
+reveal_type(nd.getfield(float))  # E: numpy.ndarray
+reveal_type(nd.getfield(float, 8))  # E: numpy.ndarray
+
+# setflags does not return a value
+# fill does not return a value