Add type annotations for @intrinsic

mypy.ini

@@ -4,7 +4,7 @@
 warn_unused_configs = True
 follow_imports = silent
 show_error_context = True
-files = **/numba/core/types/*.py, **/numba/core/datamodel/*.py, **/numba/core/rewrites/*.py, **/numba/core/unsafe/*.py, **/numba/core/rvsdg_frontend/*.py, **/numba/core/rvsdg_frontend/rvsdg/*.py
+files = **/numba/core/types/*.py, **/numba/core/extending.py, **/numba/core/datamodel/*.py, **/numba/core/rewrites/*.py, **/numba/core/unsafe/*.py, **/numba/core/rvsdg_frontend/*.py, **/numba/core/rvsdg_frontend/rvsdg/*.py
 
 # Per-module options:
 # To classify a given module as Level 1, 2 or 3 it must be added both in files (variable above) and in the lists below.

numba/_helperlib.pyi

@@ -0,0 +1,2 @@
+def _import_cython_function(module_name: str, function_name: str):
+    ...

numba/core/extending.py

@@ -4,6 +4,8 @@
 import collections
 import functools
 
+from typing import Callable, Concatenate, Generic, ParamSpec, TypeVar
+
 import numba
 from numba.core import types, errors, utils, config
 
@@ -311,18 +313,24 @@ def struct_getattr_impl(context, builder, typ, val):
         return impl_ret_borrowed(context, builder, attrty, attrval)
 
 
-class _Intrinsic(ReduceMixin):
+# Type of the parameters of the function being converted to an intrinsic,
+# excluding the typing context parameter.
+P = ParamSpec("P")
+# Return type of the function being converted to an intrinsic
+R = TypeVar("R")
+class _Intrinsic(ReduceMixin, Generic[P, R]):
     """
     Dummy callable for intrinsic
     """
-    _memo = weakref.WeakValueDictionary()
+    _memo: weakref.WeakValueDictionary = weakref.WeakValueDictionary()
+    __cache_size = config.FUNCTION_CACHE_SIZE # type: ignore
     # hold refs to last N functions deserialized, retaining them in _memo
     # regardless of whether there is another reference
-    _recent = collections.deque(maxlen=config.FUNCTION_CACHE_SIZE)
+    _recent: collections.deque = collections.deque(maxlen=__cache_size)
 
     __uuid = None
 
-    def __init__(self, name, defn, prefer_literal=False, **kwargs):
+    def __init__(self, name, defn: Callable[Concatenate[object, P], R], prefer_literal=False, **kwargs):
         self._ctor_kwargs = kwargs
         self._name = name
         self._defn = defn
@@ -360,7 +368,7 @@ def _register(self):
         infer(template)
         infer_global(self, types.Function(template))
 
-    def __call__(self, *args, **kwargs):
+    def __call__(self, *args: P.args, **kwargs: P.kwargs) -> R:
         """
         This is only defined to pretend to be a callable from CPython.
         """
@@ -395,7 +403,7 @@ def _rebuild(cls, uuid, name, defn):
             return llc
 
 
-def intrinsic(*args, **kwargs):
+def intrinsic(*args, **kwargs) -> Callable[[Callable[Concatenate[object, P], R]], Callable[P, R]]:
     """
     A decorator marking the decorated function as typing and implementing
     *func* in nopython mode using the llvmlite IRBuilder API.  This is an escape
@@ -432,7 +440,7 @@ def codegen(context, builder, signature, args):
                 return sig, codegen
     """
     # Make inner function for the actual work
-    def _intrinsic(func):
+    def _intrinsic(func: Callable[Concatenate[object, P], R]) -> Callable[P, R]:
         name = getattr(func, '__name__', str(func))
         llc = _Intrinsic(name, func, **kwargs)
         llc._register()
@@ -444,7 +452,7 @@ def _intrinsic(func):
     else:
         # options are given, create a new callable to recv the
         # definition function
-        def wrapper(func):
+        def wrapper(func: Callable[Concatenate[object, P], R]) -> Callable[P, R]:
             return _intrinsic(func)
         return wrapper