src/Pure/Isar/proof_display.ML

 
 local
 
 fun pretty_fact_name (kind, "") = Pretty.str kind
   | pretty_fact_name (kind, name) = Pretty.block [Pretty.str kind, Pretty.brk 1,
-      Pretty.str (NameSpace.base name), Pretty.str ":"];
+      Pretty.str (NameSpace.base_name name), Pretty.str ":"];
 
 fun pretty_facts ctxt =
   flat o (separate [Pretty.fbrk, Pretty.str "and "]) o
     map (single o ProofContext.pretty_fact ctxt);