remove nonce (unused)

src/grammar/mod.rs

@@ -1,6 +1,5 @@
 //! The grammar definition.
 
-pub mod nonce;
 pub mod parse_tree;
 pub mod repr;
 // pub mod token;

src/grammar/nonce.rs

@@ -1,27 +0,0 @@
-/*!
-
-A NONCE is just a guaranteed unique identifier. We use it to create
-persistent identity for alternatives as we transform the grammar.
-
-*/
-
-use std::cell::Cell;
-
-thread_local! {
-    static NONCE: Cell<u32> = Cell::new(0)
-}
-
-#[derive(Copy, Clone, PartialEq, Eq, Hash)]
-pub struct Nonce {
-    counter: u32
-}
-
-impl Nonce {
-    pub fn new() -> Nonce {
-        NONCE.with(|counter| {
-            let c = counter.get();
-            counter.set(c.checked_add(1).unwrap());
-            Nonce { counter: c }
-        })
-    }
-}