fix: do not require the runtime to use unstable features

Cargo.toml

@@ -29,9 +29,13 @@ default = [
   "log",
   "num_cpus",
   "pin-project-lite",
+  "smol",
 ]
 docs = ["attributes", "unstable", "default"]
-unstable = ["std"]
+unstable = [
+  "std",
+  "futures-timer",  
+]
 attributes = ["async-attributes"]
 std = [
   "alloc",
@@ -42,8 +46,6 @@ std = [
   "once_cell",
   "pin-utils",
   "slab",
-  "smol",
-  "futures-timer",
   "wasm-bindgen-futures",
   "futures-channel",
 ]
@@ -66,6 +68,7 @@ once_cell = { version = "1.3.1", optional = true }
 pin-project-lite = { version = "0.1.4", optional = true }
 pin-utils = { version = "0.1.0-alpha.4", optional = true }
 slab = { version = "0.4.2", optional = true }
+futures-timer = { version = "3.0.2", optional = true }
 
 # Devdepencency, but they are not allowed to be optional :/
 surf = { version = "1.0.3", optional = true }

src/future/mod.rs

@@ -61,10 +61,10 @@ cfg_std! {
     mod ready;
 }
 
-cfg_default! {
+#[cfg(any(feature = "unstable", feature = "default"))]
-    pub use timeout::{timeout, TimeoutError};
+pub use timeout::{timeout, TimeoutError};
-    mod timeout;
+#[cfg(any(feature = "unstable", feature = "default"))]
-}
+mod timeout;
 
 cfg_unstable! {
     pub use into_future::IntoFuture;

src/task/mod.rs

@@ -168,7 +168,9 @@ cfg_default! {
 }
 
 cfg_unstable! {
+    #[cfg(feature = "default")]
     pub use spawn_local::spawn_local;
 
+    #[cfg(feature = "default")]
     mod spawn_local;
 }

src/utils.rs

@@ -60,36 +60,38 @@ pub(crate) trait Context {
 }
 
 #[cfg(all(not(target_os = "unknown"), feature = "default"))]
-pub(crate) type Timer = smol::Timer;
+mod timer {
+    pub type Timer = smol::Timer;
+}
 
-#[cfg(all(target_arch = "wasm32", feature = "default"))]
+#[cfg(any(all(target_arch = "wasm32", feature = "default"), feature = "unstable"))]
-#[derive(Debug)]
+mod timer {
-pub(crate) struct Timer(futures_timer::Delay);
+    use std::pin::Pin;
+    use std::task::Poll;
 
-#[cfg(all(target_arch = "wasm32", feature = "default"))]
+    #[derive(Debug)]
-impl Timer {
+    pub(crate) struct Timer(futures_timer::Delay);
-    pub(crate) fn after(dur: std::time::Duration) -> Self {
-        Timer(futures_timer::Delay::new(dur))
-    }
-}
 
-#[cfg(target_arch = "wasm32")]
+    impl Timer {
-use std::pin::Pin;
+        pub(crate) fn after(dur: std::time::Duration) -> Self {
-#[cfg(target_arch = "wasm32")]
+            Timer(futures_timer::Delay::new(dur))
-use std::task::Poll;
+        }
+    }
 
-#[cfg(target_arch = "wasm32")]
+    impl std::future::Future for Timer {
-impl std::future::Future for Timer {
+        type Output = ();
-    type Output = ();
 
-    fn poll(mut self: Pin<&mut Self>, cx: &mut std::task::Context<'_>) -> Poll<Self::Output> {
+        fn poll(mut self: Pin<&mut Self>, cx: &mut std::task::Context<'_>) -> Poll<Self::Output> {
-        match Pin::new(&mut self.0).poll(cx) {
+            match Pin::new(&mut self.0).poll(cx) {
-            Poll::Pending => Poll::Pending,
+                Poll::Pending => Poll::Pending,
-            Poll::Ready(_) => Poll::Ready(()),
+                Poll::Ready(_) => Poll::Ready(()),
+            }
         }
     }
 }
 
+pub(crate) use timer::*;
+
 /// Defers evaluation of a block of code until the end of the scope.
 #[cfg(feature = "default")]
 #[doc(hidden)]