parser: minor refactoring

[Akim Demaille]

commit 886947c9c7d5f248860969b3e84b738602816c85
Author: Akim Demaille <akim.demai...@gmail.com>
Date:   Sun Dec 9 08:46:59 2018 +0100

    parser: minor refactoring
    
    * src/parse-gram.y (symbol.prec): Reuse int.opt.

diff --git a/src/parse-gram.y b/src/parse-gram.y
index e9aee7dd..bc8f22d7 100644
--- a/src/parse-gram.y
+++ b/src/parse-gram.y
@@ -458,16 +458,12 @@ symbols.prec:
 ;
 
 symbol.prec:
-  symbol
-    {
-      $$ = $1;
-      symbol_class_set ($1, token_sym, @1, false);
-    }
-| symbol INT
+  symbol[id] int.opt[num]
     {
-      $$ = $1;
-      symbol_class_set ($1, token_sym, @1, false);
-      symbol_user_token_number_set ($1, $2, @2);
+      $$ = $id;
+      symbol_class_set ($id, token_sym, @id, false);
+      if (0 <= $num)
+        symbol_user_token_number_set ($id, $num, @num);
     }
 ;