the feature rust_2018_preview is already implied by usage of 2018 edition.

See rust-lang/rust#53413

Author: matthiaskrgr

clippy_lints/src/lib.rs

@@ -12,7 +12,6 @@
 #![feature(iterator_find_map)]
 #![feature(macro_at_most_once_rep)]
 #![feature(tool_attributes)]
-#![feature(rust_2018_preview)]
 #![warn(rust_2018_idioms)]
 
 use toml;

src/lib.rs

@@ -1,6 +1,5 @@
 // error-pattern:cargo-clippy
 #![feature(plugin_registrar)]
-#![feature(rust_2018_preview)]
 #![feature(rustc_private)]
 #![feature(macro_vis_matcher)]
 #![allow(unknown_lints)]