use derive feature over serde_derive crate

Cargo.toml

@@ -18,9 +18,8 @@ exclude = [
 ]
 
 [dependencies]
-serde = "1.0"
+serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
-serde_derive = "1.0"
 failure = "0.1.2"
 log = "0.4.1"
 

src/diagnostics.rs

@@ -2,6 +2,8 @@
 //!
 //! The following data types are copied from [rust-lang/rust](https://github.com/rust-lang/rust/blob/de78655bca47cac8e783dbb563e7e5c25c1fae40/src/libsyntax/json.rs)
 
+use serde::Deserialize;
+
 #[derive(Clone, Deserialize, Debug, Hash, Eq, PartialEq)]
 pub struct Diagnostic {
     /// The primary error message.

src/lib.rs

@@ -7,8 +7,6 @@ extern crate failure;
 #[cfg(test)]
 #[macro_use]
 extern crate proptest;
-#[macro_use]
-extern crate serde_derive;
 use serde_json;
 
 use std::collections::HashSet;