Waker and LocalWaker docs: Make the warning much more specific.

Author: ijackson

library/core/src/task/wake.rs

@@ -543,11 +543,12 @@ impl Waker {
     ///
     /// # Warning
     ///
-    /// Do not use this function as a way to be able to call `poll` methods in production code
-    /// from within a non-`async`, non-`poll`, function.
+    /// When implementing a runtime-agnostic future which wraps other future(s),
+    /// do not use this function as a way to be able to call `poll` methods
+    /// when you don't have your caller's `Context` available.
     ///
     /// Using a no-op waker for that purpose would cause wakeups to be lost:
-    /// the future would store only the no-op waker,
+    /// the inner future would store only the no-op waker,
     /// replacing the proper waker for the waiting task.
     ///
     /// # Examples
@@ -809,12 +810,12 @@ impl LocalWaker {
     ///
     /// # Warning
     ///
-    /// Do not use this function as a way to be able to call `poll` methods,
-    /// in production code,
-    /// from within a non-`async`, non-`poll`, function.
+    /// When implementing a runtime-agnostic future which wraps other future(s),
+    /// do not use this function as a way to be able to call `poll` methods
+    /// when you don't have your caller's `Context` available.
     ///
     /// Using a no-op waker for that purpose would cause wakeups to be lost:
-    /// the future would store only the no-op waker,
+    /// the inner future would store only the no-op waker,
     /// replacing the proper waker for the waiting task.
     ///
     /// # Examples