Anchor added to a source word w ill now also be set as its shadow.

umbra/words.py

@@ -201,6 +201,7 @@ class SourceWord(Word):
 
     def _set_anchor(self, anchor):
         self._anchor = anchor
+        self._shadow = anchor
 
     @property
     def shadow(self):
@@ -236,6 +237,7 @@ class SourceWord(Word):
         """
         return other.onset - self._onset
 
+
 class Sentence(list):
     def __init__(self, words):
         super().__init__(words)