Weaken guarantee for From<legacy::RangeInclusive> for RangeInclusive

library/core/src/range.rs

@@ -402,7 +402,8 @@ const impl<T> From<legacy::RangeInclusive<T>> for RangeInclusive<T> {
     ///
     /// # Panics
     ///
-    /// Panics if the legacy range iterator has been exhausted.
+    /// If the legacy range iterator has been exhausted,
+    /// this function will either panic or return an empty range.
     ///
     /// # Examples
     ///
@@ -419,19 +420,23 @@ const impl<T> From<legacy::RangeInclusive<T>> for RangeInclusive<T> {
     /// assert_eq!((empty.start, empty.last), (0, 0));
     /// ```
     ///
-    /// ```should_panic
+    /// ```
+    /// # // This test requires unwinding to work.
+    /// # // Disable it when unwinding isn't available.
+    /// # #[cfg(panic = "unwind")]
+    /// # fn main() {
     /// use core::range::legacy;
     /// use core::range::RangeInclusive;
+    /// use std::panic::catch_unwind;
     ///
     /// let mut exhausted: legacy::RangeInclusive<i32> = 0..=0;
     /// exhausted.next();
-    /// # if exhausted.is_empty() {
-    /// # // assert!s don't work correctly in `should_panic` doctests since you
-    /// # // can't assert the panic message. Skip the rest of the test instead,
-    /// # // so that the expected panic doesn't happen and the test fails.
-    /// assert!(exhausted.is_empty());
-    /// let _ = RangeInclusive::from(exhausted); // this panics
+    /// let result = catch_unwind(|| RangeInclusive::from(exhausted));
+    /// // The `from` call either panicked or returned an empty range.
+    /// assert!(result.is_err() || result.is_ok_and(|range| range.is_empty()));
     /// # }
+    /// # #[cfg(not(panic = "unwind"))]
+    /// # fn main() {}
     /// ```
     #[inline]
     fn from(value: legacy::RangeInclusive<T>) -> Self {