Make the dispatch function more explicit for type checkers with @overload

check_linter_assertions.py

@@ -158,7 +158,7 @@ def run_linter(linter: str) -> str:
         str: `stdout`.
     """
     p = subprocess.Popen(
-        [linter, source_dir],
+        [sys.executable, "-m", linter, source_dir],
         stdout=subprocess.PIPE,
         stderr=subprocess.PIPE,
     )

plum/dispatcher.py

@@ -1,4 +1,4 @@
-from typing import Any, Callable, Dict, Optional, Tuple, TypeVar, Union
+from typing import Any, Callable, Dict, Optional, Tuple, TypeVar, Union, overload
 
 from .function import Function
 from .overload import get_overloads
@@ -23,7 +23,21 @@ def __init__(self):
         self.functions: Dict[str, Function] = {}
         self.classes: Dict[str, Dict[str, Function]] = {}
 
-    def __call__(self, method: Optional[T] = None, precedence: int = 0) -> T:
+    @overload
+    def __call__(self, method: Callable[[Any], Any], precedence: int = 0) -> Function:
+        ...
+
+    @overload
+    def __call__(
+        self, method: None, precedence: int = 0
+    ) -> Callable[[Callable[[Any], Any]], Function]:
+        ...
+
+    def __call__(
+        self,
+        method: Optional[Callable[[Any], Any]] = None,
+        precedence: int = 0,
+    ) -> Union[Function, Callable[[Callable[[Any], Any]], Function]]:
         """Decorator to register for a particular signature.
 
         Args:

plum/function.py

@@ -388,7 +388,7 @@ def _handle_not_found_lookup_error(
             raise ex
         return method, return_type
 
-    def __call__(self, *args, **kw_args):
+    def __call__(self, *args: object, **kw_args: object):
         method, return_type = self._resolve_method_with_cache(args=args)
         return _convert(method(*args, **kw_args), return_type)