Merging upstream version 1.67.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/library/std/src/time/tests.rs b/library/std/src/time/tests.rs
index 6229556c8..2e64ae59a 100644
--- a/library/std/src/time/tests.rs
+++ b/library/std/src/time/tests.rs
@@ -88,6 +88,14 @@ fn instant_math_is_associative() {
     // Changing the order of instant math shouldn't change the results,
     // especially when the expression reduces to X + identity.
     assert_eq!((now + offset) - now, (now - now) + offset);
+
+    // On any platform, `Instant` should have the same resolution as `Duration` (e.g. 1 nanosecond)
+    // or better. Otherwise, math will be non-associative (see #91417).
+    let now = Instant::now();
+    let provided_offset = Duration::from_nanos(1);
+    let later = now + provided_offset;
+    let measured_offset = later - now;
+    assert_eq!(measured_offset, provided_offset);
 }
 
 #[test]