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, 67 insertions, 0 deletions

diff --git a/numpy/tests/fail/scalars.py b/numpy/tests/fail/scalars.py
new file mode 100644
index 000000000..0dfc55124
--- /dev/null
+++ b/numpy/tests/fail/scalars.py
@@ -0,0 +1,67 @@
+import numpy as np
+
+# Construction
+
+np.float32(3j)  # E: incompatible type
+
+# Technically the following examples are valid NumPy code. But they
+# are not considered a best practice, and people who wish to use the
+# stubs should instead do
+#
+# np.array([1.0, 0.0, 0.0], dtype=np.float32)
+# np.array([], dtype=np.complex64)
+#
+# See e.g. the discussion on the mailing list
+#
+# https://mail.python.org/pipermail/numpy-discussion/2020-April/080566.html
+#
+# and the issue
+#
+# https://github.com/numpy/numpy-stubs/issues/41
+#
+# for more context.
+np.float32([1.0, 0.0, 0.0])  # E: incompatible type
+np.complex64([])  # E: incompatible type
+
+np.complex64(1, 2)  # E: Too many arguments
+# TODO: protocols (can't check for non-existent protocols w/ __getattr__)
+
+np.datetime64(0)  # E: non-matching overload
+
+dt_64 = np.datetime64(0, "D")
+td_64 = np.timedelta64(1, "h")
+
+dt_64 + dt_64  # E: Unsupported operand types
+
+td_64 - dt_64  # E: Unsupported operand types
+td_64 / dt_64  # E: No overload
+td_64 % 1  # E: Unsupported operand types
+td_64 % dt_64  # E: Unsupported operand types
+
+
+class A:
+    def __float__(self):
+        return 1.0
+
+
+np.int8(A())  # E: incompatible type
+np.int16(A())  # E: incompatible type
+np.int32(A())  # E: incompatible type
+np.int64(A())  # E: incompatible type
+np.uint8(A())  # E: incompatible type
+np.uint16(A())  # E: incompatible type
+np.uint32(A())  # E: incompatible type
+np.uint64(A())  # E: incompatible type
+
+np.void("test")  # E: incompatible type
+
+np.generic(1)  # E: Cannot instantiate abstract class
+np.number(1)  # E: Cannot instantiate abstract class
+np.integer(1)  # E: Cannot instantiate abstract class
+np.signedinteger(1)  # E: Cannot instantiate abstract class
+np.unsignedinteger(1)  # E: Cannot instantiate abstract class
+np.inexact(1)  # E: Cannot instantiate abstract class
+np.floating(1)  # E: Cannot instantiate abstract class
+np.complexfloating(1)  # E: Cannot instantiate abstract class
+np.character("test")  # E: Cannot instantiate abstract class
+np.flexible(b"test")  # E: Cannot instantiate abstract class