fix annotation writing after changing source position comments

Cython/Compiler/Annotate.py

@@ -44,7 +44,7 @@ class AnnotationCCodeWriter(CCodeWriter):
         if pos is not None:
             CCodeWriter.mark_pos(self, pos)
         if self.last_pos:
-            pos_code = self.code.setdefault(self.last_pos[0].get_description(),{})
+            pos_code = self.code.setdefault(self.last_pos[0].filename,{})
             code = pos_code.get(self.last_pos[1], "")
             pos_code[self.last_pos[1]] = code + self.annotation_buffer.getvalue()
         self.annotation_buffer = StringIO()

Cython/Compiler/Scanning.py

@@ -200,6 +200,8 @@ class StringSourceDescriptor(SourceDescriptor):
     Instances of this class can be used instead of a filenames if the
     code originates from a string object.
     """
+    filename = None
+
     def __init__(self, name, code):
         self.name = name
         #self.set_file_type_from_name(name)