fix the issue with function visibility

tokio/src/coop.rs

@@ -104,7 +104,7 @@ fn with_budget<R>(budget: Budget, f: impl FnOnce() -> R) -> R {
     f()
 }
 
-cfg_rt! {
+cfg_pub_if_rt! {
     /// Returns `true` if there is still budget left on the task.
     ///
     /// Futures created by the tokio library functions are budget-aware and yield when there is no more
@@ -191,7 +191,7 @@ cfg_rt! {
     /// # }
     ///```
     #[inline(always)]
-    pub fn has_budget_remaining() -> bool {
+    fn has_budget_remaining() -> bool {
         // If the current budget cannot be accessed due to the thread-local being
         // shutdown, then we assume there is budget remaining.
         context::budget(|cell| cell.get().has_remaining()).unwrap_or(true)

tokio/src/macros/cfg.rs

@@ -549,6 +549,20 @@ macro_rules! cfg_not_coop {
     }
 }
 
+macro_rules! cfg_pub_if_rt {
+    ($($(#[$meta:meta])* fn $($inner:tt)*)*) => {
+        $(
+            $(#[$meta])*
+            #[cfg(feature = "rt")]
+            pub fn $($inner)*
+
+            $(#[$meta])*
+            #[cfg(not(feature = "rt"))]
+            pub(crate) fn $($inner)*
+        )*
+    }
+}
+
 macro_rules! cfg_has_atomic_u64 {
     ($($item:item)*) => {
         $(