Update codegen to 2018 edition
diff --git a/codegen/src/parse.rs b/codegen/src/parse.rs
index eff8539..08aefd1 100644
--- a/codegen/src/parse.rs
+++ b/codegen/src/parse.rs
@@ -1,7 +1,8 @@
 use crate::types;
 
 use indexmap::IndexMap;
-use syn::{Data, DataStruct, DeriveInput, Ident, Item};
+use quote::quote;
+use syn::{parse_quote, Data, DataStruct, DeriveInput, Ident, Item};
 
 use std::collections::BTreeMap;
 use std::fs::File;
@@ -246,6 +247,7 @@
     use crate::types;
 
     use proc_macro2::TokenStream;
+    use quote::quote;
     use syn;
     use syn::parse::{Parse, ParseStream, Result};
     use syn::*;