Added Warning and Exception annotations (#57)

See https://github.com/numpy/numpy-stubs/issues/54.

Added annotations and tests for:
* np.ModuleDeprecationWarning
* np.VisibleDeprecationWarning
* np.ComplexWarning
* np.RankWarning
* np.TooHardError
* np.AxisError

numpy-stubs/__init__.pyi

@@ -103,7 +103,7 @@ class dtype:
     def descr(self) -> List[Union[Tuple[str, str], Tuple[str, str, _Shape]]]: ...
     @property
     def fields(
-        self
+        self,
     ) -> Optional[Mapping[str, Union[Tuple[dtype, int], Tuple[dtype, int, Any]]]]: ...
     @property
     def flags(self) -> int: ...
@@ -778,3 +778,17 @@ trunc: ufunc
 
 # TODO(shoyer): remove when the full numpy namespace is defined
 def __getattr__(name: str) -> Any: ...
+
+# Warnings
+class ModuleDeprecationWarning(DeprecationWarning): ...
+class VisibleDeprecationWarning(UserWarning): ...
+class ComplexWarning(RuntimeWarning): ...
+class RankWarning(UserWarning): ...
+
+# Errors
+class TooHardError(RuntimeError): ...
+
+class AxisError(ValueError, IndexError):
+    def __init__(
+        self, axis: int, ndim: Optional[int] = ..., msg_prefix: Optional[str] = ...
+    ) -> None: ...

tests/fail/warnings_and_errors.py

@@ -0,0 +1,5 @@
+import numpy as np
+
+np.AxisError(1.0)  # E: Argument 1 to "AxisError" has incompatible type
+np.AxisError(1, ndim=2.0)  # E: Argument "ndim" to "AxisError" has incompatible type
+np.AxisError(2, msg_prefix=404)  # E: Argument "msg_prefix" to "AxisError" has incompatible type

tests/pass/warnings_and_errors.py

@@ -0,0 +1,7 @@
+import numpy as np
+
+np.AxisError(1)
+np.AxisError(1, ndim=2)
+np.AxisError(1, ndim=None)
+np.AxisError(1, ndim=2, msg_prefix='error')
+np.AxisError(1, ndim=2, msg_prefix=None)

tests/reveal/warnings_and_errors.py

@@ -0,0 +1,10 @@
+from typing import Type
+
+import numpy as np
+
+reveal_type(np.ModuleDeprecationWarning())  # E: numpy.ModuleDeprecationWarning
+reveal_type(np.VisibleDeprecationWarning())  # E: numpy.VisibleDeprecationWarning
+reveal_type(np.ComplexWarning())  # E: numpy.ComplexWarning
+reveal_type(np.RankWarning())  # E: numpy.RankWarning
+reveal_type(np.TooHardError())  # E: numpy.TooHardError
+reveal_type(np.AxisError(1))  # E: numpy.AxisError