src/Pure/Isar/isar_syn.ML

 
 (* translations *)
 
 val trans_pat =
   Scan.optional
-    (@{keyword "("} |-- Parse.!!! (Parse.xname --| @{keyword ")"})) "logic"
+    (@{keyword "("} |-- Parse.!!! (Parse.inner_syntax Parse.xname --| @{keyword ")"})) "logic"
     -- Parse.inner_syntax Parse.string;
 
 fun trans_arrow toks =
   ((@{keyword "\<rightharpoonup>"} || @{keyword "=>"}) >> K Syntax.Parse_Rule ||
     (@{keyword "\<leftharpoondown>"} || @{keyword "<="}) >> K Syntax.Print_Rule ||