modernize some files

crates/ra_syntax/Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-edition = "2015"
+edition = "2018"
 name = "ra_syntax"
 version = "0.1.0"
 authors = ["Aleksey Kladov <aleksey.kladov@gmail.com>"]

crates/ra_syntax/src/lib.rs

@@ -20,13 +20,6 @@
 #![allow(missing_docs)]
 //#![warn(unreachable_pub)] // rust-lang/rust#47816
 
-extern crate arrayvec;
-extern crate drop_bomb;
-extern crate itertools;
-extern crate parking_lot;
-extern crate rowan;
-extern crate unicode_xid;
-
 #[cfg(test)]
 #[macro_use]
 extern crate test_utils;
@@ -48,11 +41,11 @@ pub mod utils;
 mod validation;
 mod yellow;
 
+pub use rowan::{SmolStr, TextRange, TextUnit};
 pub use crate::{
     ast::AstNode,
     lexer::{tokenize, Token},
     reparsing::AtomEdit,
-    rowan::{SmolStr, TextRange, TextUnit},
     syntax_kinds::SyntaxKind,
     yellow::{
         Direction, OwnedRoot, RefRoot, SyntaxError, SyntaxNode, SyntaxNodeRef, TreeRoot, WalkEvent, Location,

crates/ra_syntax/src/parser_api.rs

@@ -1,5 +1,6 @@
+use drop_bomb::DropBomb;
+
 use crate::{
-    drop_bomb::DropBomb,
     parser_impl::ParserImpl,
     token_set::TokenSet,
     SyntaxKind::{self, ERROR},