Fix subtraction of Instants

Author: jhpratt

CHANGELOG.md

@@ -7,7 +7,14 @@ Versioning].
 
 ---
 
-## Unreleased
+## 0.2.12 [2020-04-30]
+
+### Fixed
+
+Subtracting `Instant`s can correctly result in a negative duration, rather than
+resulting in the absolute value of it.
+
+## 0.2.11 [2020-04-27]
 
 ### Added
 

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "time"
-version = "0.2.11"
+version = "0.2.12"
 authors = ["Jacob Pratt <[email protected]>"]
 edition = "2018"
 repository = "https://github.com/time-rs/time"

src/instant.rs

@@ -154,8 +154,7 @@ impl Sub for Instant {
             Ordering::Greater => (self.inner - other.inner)
                 .try_into()
                 .expect("overflow converting `std::time::Duration` to `time::Duration`"),
-            Ordering::Less => (other.inner - self.inner)
-                .try_into()
+            Ordering::Less => -Duration::try_from(other.inner - self.inner)
                 .expect("overflow converting `std::time::Duration` to `time::Duration`"),
         }
     }
@@ -496,4 +495,19 @@ mod test {
         let now_std = StdInstant::from(now_time) - 1.seconds();
         assert!(now_std < now_time);
     }
+
+    #[test]
+    fn sub_regression() {
+        let now = Instant::now();
+        let future = now + Duration::seconds(5);
+        let past = now - Duration::seconds(5);
+
+        assert_eq!(future - now, Duration::seconds(5));
+        assert_eq!(now - past, Duration::seconds(5));
+        assert_eq!(future - past, Duration::seconds(10));
+
+        assert_eq!(now - future, Duration::seconds(-5));
+        assert_eq!(past - now, Duration::seconds(-5));
+        assert_eq!(past - future, Duration::seconds(-10));
+    }
 }