Update to 2021 edition

Author: dtolnay

Cargo.toml

@@ -5,7 +5,7 @@ authors = ["David Tolnay <[email protected]>"]
 categories = ["asynchronous", "no-std"]
 description = "Type erasure for async trait methods"
 documentation = "https://docs.rs/async-trait"
-edition = "2018"
+edition = "2021"
 keywords = ["async"]
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/dtolnay/async-trait"

src/receiver.rs

@@ -1,5 +1,4 @@
 use proc_macro2::{Group, Span, TokenStream, TokenTree};
-use std::iter::FromIterator;
 use syn::visit_mut::{self, VisitMut};
 use syn::{
     Block, ExprPath, Ident, Item, Macro, Pat, PatIdent, Path, Receiver, Signature, Token, TypePath,

tests/test.rs

@@ -873,7 +873,7 @@ pub mod issue89 {
     }
 
     #[async_trait]
-    impl Trait for Send + Sync {
+    impl Trait for dyn Send + Sync {
         async fn f(&self) {}
     }