feat: Make the task module no_std

Cargo.toml

@@ -39,7 +39,6 @@ unstable = ["std", "broadcaster", "futures-timer"]
 attributes = ["async-attributes"]
 std = [
   "crossbeam-utils",
-  "futures-core",
   "futures-io",
   "memchr",
   "once_cell",
@@ -48,7 +47,9 @@ std = [
   "slab",
   "no-std",
 ]
-no-std = []
+no-std = [
+  "futures-core",
+]
 
 [dependencies]
 async-attributes = { version = "1.1.1", optional = true }

src/lib.rs

@@ -241,6 +241,10 @@ pub use async_attributes::{main, test};
 #[cfg(feature = "std")]
 mod macros;
 
+cfg_no_std! {
+    pub mod task;
+}
+
 cfg_std! {
     pub mod future;
     pub mod io;
@@ -248,7 +252,6 @@ cfg_std! {
     pub mod prelude;
     pub mod stream;
     pub mod sync;
-    pub mod task;
 }
 
 cfg_default! {

src/task/mod.rs

@@ -117,13 +117,16 @@
 //! [`task_local!`]: ../macro.task_local.html
 //! [`with`]: struct.LocalKey.html#method.with
 
-cfg_std! {
+cfg_no_std! {
     #[doc(inline)]
-    pub use std::task::{Context, Poll, Waker};
-
+    pub use core::task::{Context, Poll, Waker};
     pub use ready::ready;
-    pub use yield_now::yield_now;
+
     mod ready;
+}
+
+cfg_std! {
+    pub use yield_now::yield_now;
     mod yield_now;
 }