diff -r a39baba12732 -r 68751fe1c036 src/Pure/PIDE/prover.scala
--- a/src/Pure/PIDE/prover.scala	Tue Aug 02 18:44:37 2016 +0200
+++ b/src/Pure/PIDE/prover.scala	Tue Aug 02 18:45:34 2016 +0200
@@ -13,19 +13,6 @@
 
 object Prover
 {
-  /* syntax */
-
-  trait Syntax
-  {
-    def ++ (other: Syntax): Syntax
-    def add_keywords(keywords: Thy_Header.Keywords): Syntax
-    def add_abbrevs(abbrevs: Thy_Header.Abbrevs): Syntax
-    def parse_spans(input: CharSequence): List[Command_Span.Span]
-    def load_command(name: String): Option[List[String]]
-    def load_commands_in(text: String): Boolean
-  }
-
-
   /* underlying system process */
 
   trait System_Process