got rid of unused libraries, including raw, and got rid of warnings

build.rs

@@ -1,10 +1,5 @@
-use std::convert::TryInto;
 use std::env;
-use std::env::VarError;
 use std::error::Error;
-use std::fs::{read_dir, DirEntry, File};
-use std::io::Write;
-use std::path::Path;
 use std::process::Command;
 
 fn main() {
@@ -33,14 +28,14 @@ fn gen_for_grammar(
     grammar_file_name: &str,
     antlr_path: &str,
     additional_arg: Option<&str>,
-) -> Result<(), Box<Error>> {
+) -> Result<(), Box<dyn Error>> {
     // let out_dir = env::var("OUT_DIR").unwrap();
     // let dest_path = Path::new(&out_dir);
 
     let input = env::current_dir().unwrap().join("grammars");
     let file_name = grammar_file_name.to_owned() + ".g4";
 
-    let c = Command::new("java")
+    let _c = Command::new("java")
         .current_dir(input)
         .arg("-cp")
         .arg(antlr_path)

src/atn_config_set.rs

@@ -14,6 +14,7 @@ use crate::parser_atn_simulator::MergeCache;
 use crate::prediction_context::{MurmurHasherBuilder, PredictionContext};
 use crate::semantic_context::SemanticContext;
 
+#[allow(dead_code)]
 pub struct ATNConfigSet {
     cached_hash: u64,
 

src/lib.rs

@@ -1,7 +1,6 @@
 #![crate_type = "lib"]
 #![feature(try_blocks)]
 //#![feature(nll)]
-#![feature(raw)]
 #![feature(is_sorted)]
 #![feature(cell_update)]
 #![feature(get_mut_unchecked)]
@@ -13,7 +12,7 @@
 // #![feature(generic_associated_types)]
 #![warn(rust_2018_idioms)]
 #![warn(missing_docs)] // warn if there is missing docs
-#![warn(missing_debug_implementations)]
+//#![warn(missing_debug_implementations)] there are missing debugs
 #![warn(trivial_numeric_casts)]
 #![allow(incomplete_features)]