src/Pure/System/isabelle_system.scala

     if (gnutar_check) bash("tar " + options + args, redirect = redirect)
     else error("Expected to find GNU tar executable")
   }
 
   def make_patch(base_dir: Path, src: Path, dst: Path, diff_options: String = ""): String = {
-    with_tmp_file("patch")(patch => {
+    with_tmp_file("patch") { patch =>
       Isabelle_System.bash(
         "diff -ru " + diff_options + " -- " + File.bash_path(src) + " " + File.bash_path(dst) +
           " > " + File.bash_path(patch),
         cwd = base_dir.file).check_rc(_ <= 1)
       File.read(patch)
-    })
+    }
   }
 
   def hostname(): String = bash("hostname -s").check.out
 
   def open(arg: String): Unit =