src/Pure/PIDE/resources.scala

       doc_blobs: Document.Blobs,
       edits: List[Document.Edit_Text],
       consolidate: List[Document.Node.Name]): Session.Change =
     Thy_Syntax.parse_change(resources, reparse_limit, previous, doc_blobs, edits, consolidate)
 
-  def commit(change: Session.Change) { }
+  def commit(change: Session.Change): Unit = {}
 
 
   /* theory and file dependencies */
 
   def dependencies(