diff --git a/lark/exceptions.py b/lark/exceptions.py
index 0dfb659..6f7d32d 100644
--- a/lark/exceptions.py
+++ b/lark/exceptions.py
@@ -12,7 +12,7 @@ class ConfigurationError(LarkError, ValueError):
     pass
 
 
-def assert_config(value, options, msg='Got %r, expected one of %s'):
+def assert_config(value, options: list, msg='Got %r, expected one of %s'):
     if value not in options:
         raise ConfigurationError(msg % (value, options))
 
diff --git a/lark/lexer.py b/lark/lexer.py
index a017001..36ed6bc 100644
--- a/lark/lexer.py
+++ b/lark/lexer.py
@@ -130,7 +130,7 @@ class Token(str):
             inst = super(Token, cls).__new__(cls, value)
 
         inst.type = type_
-        inst.start_pos = start_pos if start_pos is not None else pos_in_stream
+        inst.start_pos = start_pos
         inst.value = value
         inst.line = line
         inst.column = column
@@ -287,7 +287,7 @@ class Scanner:
                 return m.group(0), type_from_index[m.lastindex]
 
 
-def _regexp_has_newline(r):
+def _regexp_has_newline(r: str):
     r"""Expressions that may indicate newlines in a regexp:
         - newlines (\n)
         - escaped newline (\\n)