make it clear that Range cannot represent arbitrary ranges

library/core/src/ops/range.rs

@@ -56,6 +56,10 @@ impl fmt::Debug for RangeFull {
 /// The range `start..end` contains all values with `start <= x < end`.
 /// It is empty if `start >= end`.
 ///
+/// Note that this type is not suited to represent all possible ranges. For example, `Range<u8>`
+/// cannot represent the range that covers all of `u8`. Use [`(Bound<T>, Bound<T>)`][Bound] if you
+/// need a type that can store an arbitrary range.
+///
 /// # Examples
 ///
 /// The `start..end` syntax is a `Range`:

library/core/src/range.rs

@@ -48,6 +48,10 @@ pub use crate::ops::{RangeFull, RangeTo};
 /// The `Range` contains all values with `start <= x < end`.
 /// It is empty if `start >= end`.
 ///
+/// Note that this type is not suited to represent all possible ranges. For example, `Range<u8>`
+/// cannot represent the range that covers all of `u8`. Use [`(Bound<T>, Bound<T>)`][Bound] if you
+/// need a type that can store an arbitrary range.
+///
 /// # Examples
 ///
 /// ```