web: More accurate typing for get_{body,query}_argument()

Use the same overload technique as get_argument().

Fixes tornadoweb#3336

tornado/web.py

@@ -470,7 +470,23 @@ def get_arguments(self, name: str, strip: bool = True) -> List[str]:
 
  return self._get_arguments(name, self.request.arguments, strip)
 
- def get_body_argument(
+ @overload
+ def get_body_argument(self, name: str, default: str, strip: bool = True) -> str:
+ pass
+
+ @overload
+ def get_body_argument( # noqa: F811
+ self, name: str, default: _ArgDefaultMarker = _ARG_DEFAULT, strip: bool = True
+ ) -> str:
+ pass
+
+ @overload
+ def get_body_argument( # noqa: F811
+ self, name: str, default: None, strip: bool = True
+ ) -> Optional[str]:
+ pass
+
+ def get_body_argument( # noqa: F811
  self,
  name: str,
  default: Union[None, str, _ArgDefaultMarker] = _ARG_DEFAULT,
@@ -498,7 +514,23 @@ def get_body_arguments(self, name: str, strip: bool = True) -> List[str]:
  """
  return self._get_arguments(name, self.request.body_arguments, strip)
 
- def get_query_argument(
+ @overload
+ def get_query_argument(self, name: str, default: str, strip: bool = True) -> str:
+ pass
+
+ @overload
+ def get_query_argument( # noqa: F811
+ self, name: str, default: _ArgDefaultMarker = _ARG_DEFAULT, strip: bool = True
+ ) -> str:
+ pass
+
+ @overload
+ def get_query_argument( # noqa: F811
+ self, name: str, default: None, strip: bool = True
+ ) -> Optional[str]:
+ pass
+
+ def get_query_argument( # noqa: F811
  self,
  name: str,
  default: Union[None, str, _ArgDefaultMarker] = _ARG_DEFAULT,