Migrate sr-primitives, sr-sandbox, sr-std and sr-version to the 2018 edition (#1694)

substrate/core/sr-std/Cargo.toml

@@ -3,6 +3,7 @@ name = "sr-std"
 version = "0.1.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 build = "build.rs"
+edition = "2018"
 
 [build-dependencies]
 rustc_version = "0.2"

substrate/core/sr-std/build.rs

@@ -1,6 +1,5 @@
 //! Set a nightly feature
 
-extern crate rustc_version;
 use rustc_version::{version, version_meta, Channel};
 
 fn main() {

substrate/core/sr-std/src/lib.rs

@@ -41,13 +41,13 @@ include!("../without_std.rs");
 ///
 /// This should include only things which are in the normal std prelude.
 pub mod prelude {
-	pub use ::vec::Vec;
-	pub use ::boxed::Box;
-	pub use ::cmp::{Eq, PartialEq};
-	pub use ::clone::Clone;
+	pub use crate::vec::Vec;
+	pub use crate::boxed::Box;
+	pub use crate::cmp::{Eq, PartialEq};
+	pub use crate::clone::Clone;
 
 	// Re-export `vec!` macro here, but not in `std` mode, since
 	// std's prelude already brings `vec!` into the scope.
 	#[cfg(not(feature = "std"))]
-	pub use ::vec;
+	pub use crate::vec;
 }