Use correct line number with decorators on Python 3.8

Author: domdfcoding

flake8_missing_annotations/__init__.py

@@ -28,6 +28,7 @@
 
 # stdlib
 import ast
+import sys
 import textwrap
 from typing import Any, Generator, Iterable, List, NamedTuple, Optional, Tuple, Type
 
@@ -260,10 +261,16 @@ def visit_FunctionDef(self, function: ast.FunctionDef) -> None:
 			if self._state:
 				function_name = '.'.join((*self._state, function_name))
 
+			function_lineno = function.lineno
+
+			if sys.version_info < (3, 8):
+				# TODO: account for multiline decorators
+				function_lineno += len(decorators)
+
 			error = Error(
 					function_name,
 					offending_arguments,
-					function.lineno + len(decorators),
+					function_lineno,
 					function.col_offset,
 					)
 			self._errors.append(error)