Remove use of alloc_prelude feature

Author: taiki-e

futures-util/src/future/join_all.rs

@@ -7,7 +7,8 @@ use core::iter::FromIterator;
 use core::mem;
 use core::pin::Pin;
 use core::task::{Context, Poll};
-use alloc::prelude::v1::*;
+use alloc::boxed::Box;
+use alloc::vec::Vec;
 
 #[derive(Debug)]
 enum ElemState<F>

futures-util/src/lib.rs

@@ -5,7 +5,7 @@
 #![cfg_attr(feature = "alloc", feature(box_into_pin))]
 #![cfg_attr(feature = "std", feature(async_await, await_macro))]
 #![cfg_attr(feature = "cfg-target-has-atomic", feature(cfg_target_has_atomic))]
-#![cfg_attr(all(feature = "alloc", not(feature = "std")), feature(alloc, alloc_prelude))]
+#![cfg_attr(all(feature = "alloc", not(feature = "std")), feature(alloc))]
 
 #![cfg_attr(not(feature = "std"), no_std)]
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]

futures-util/src/stream/chunks.rs

@@ -5,7 +5,7 @@ use futures_sink::Sink;
 use pin_utils::{unsafe_pinned, unsafe_unpinned};
 use core::mem;
 use core::pin::Pin;
-use alloc::prelude::v1::*;
+use alloc::vec::Vec;
 
 /// Stream for the [`chunks`](super::StreamExt::chunks) method.
 #[derive(Debug)]

futures-util/src/try_future/try_join_all.rs

@@ -7,7 +7,8 @@ use core::iter::FromIterator;
 use core::mem;
 use core::pin::Pin;
 use core::task::{Context, Poll};
-use alloc::prelude::v1::*;
+use alloc::boxed::Box;
+use alloc::vec::Vec;
 
 use super::TryFuture;