Fix stage0 core tests

Author: oli-obk

library/core/src/iter/sources/from_coroutine.rs

@@ -11,7 +11,8 @@ use crate::pin::Pin;
 /// # Examples
 ///
 /// ```
-/// #![feature(coroutines)]
+/// #![cfg_attr(bootstrap, feature(generators))]
+/// #![cfg_attr(not(bootstrap), feature(coroutines))]
 /// #![feature(iter_from_coroutine)]
 ///
 /// let it = std::iter::from_coroutine(|| {

library/core/src/ops/coroutine.rs

@@ -40,7 +40,9 @@ pub enum CoroutineState<Y, R> {
 /// closure-like:
 ///
 /// ```rust
-/// #![feature(coroutines, coroutine_trait)]
+/// #![cfg_attr(bootstrap, feature(generators))]
+/// #![cfg_attr(not(bootstrap), feature(coroutines))]
+/// #![feature(coroutine_trait)]
 ///
 /// use std::ops::{Coroutine, CoroutineState};
 /// use std::pin::Pin;

library/core/src/pin.rs

@@ -1088,7 +1088,9 @@ impl<P, U> DispatchFromDyn<Pin<U>> for Pin<P> where P: DispatchFromDyn<U> {}
 /// ### With `Coroutine`s
 ///
 /// ```rust
-/// #![feature(coroutines, coroutine_trait)]
+/// #![cfg_attr(bootstrap, feature(generators))]
+/// #![cfg_attr(not(bootstrap), feature(coroutines))]
+/// #![feature(coroutine_trait)]
 /// use core::{
 ///     ops::{Coroutine, CoroutineState},
 ///     pin::pin,