Auto merge of #87781 - est31:remove_box, r=oli-obk

Remove box syntax from compiler and tools

Removes box syntax from the compiler and tools. In #49733, the future of box syntax is uncertain and the use in the compiler was listed as one of the reasons to keep it. Removal of box syntax [might affect the code generated](https://github.com/rust-lang/rust/pull/49646#issuecomment-379219615) and slow down the compiler so I'd recommend doing a perf run on this.

2 files changed, 1 insertions, 2 deletions

diff --git a/compiler/rustc_serialize/src/lib.rs b/compiler/rustc_serialize/src/lib.rs
index c79786a839f..b31fbab20ac 100644
--- a/compiler/rustc_serialize/src/lib.rs
+++ b/compiler/rustc_serialize/src/lib.rs
@@ -9,7 +9,6 @@ Core encoding and decoding interfaces.
     html_playground_url = "https://play.rust-lang.org/",
     test(attr(allow(unused_variables), deny(warnings)))
 )]
-#![feature(box_syntax)]
 #![feature(never_type)]
 #![feature(nll)]
 #![feature(associated_type_bounds)]
diff --git a/compiler/rustc_serialize/src/serialize.rs b/compiler/rustc_serialize/src/serialize.rs
index bb3c537ef19..4d9aaaecec8 100644
--- a/compiler/rustc_serialize/src/serialize.rs
+++ b/compiler/rustc_serialize/src/serialize.rs
@@ -679,6 +679,6 @@ impl<S: Encoder, T: ?Sized + Encodable<S>> Encodable<S> for Box<T> {
 }
 impl<D: Decoder, T: Decodable<D>> Decodable<D> for Box<T> {
     fn decode(d: &mut D) -> Result<Box<T>, D::Error> {
-        Ok(box Decodable::decode(d)?)
+        Ok(Box::new(Decodable::decode(d)?))
     }
 }