Handle negative numbers in `sqrt` properly.

Closes #9987.

2 files changed, 22 insertions, 0 deletions

diff --git a/src/libstd/num/f32.rs b/src/libstd/num/f32.rs
index b2a9f1b7b20..f98e81bb2c8 100644
--- a/src/libstd/num/f32.rs
+++ b/src/libstd/num/f32.rs
@@ -787,4 +787,15 @@ mod tests {
         assert_eq!(NEG_INFINITY.integer_decode(), (8388608u64, 105i16, -1i8));
         assert_eq!(NAN.integer_decode(), (12582912u64, 105i16, 1i8));
     }
+
+    #[test]
+    fn test_sqrt_domain() {
+        assert!(NAN.sqrt().is_nan());
+        assert!(NEG_INFINITY.sqrt().is_nan());
+        assert!((-1.0f32).sqrt().is_nan());
+        assert_eq!((-0.0f32).sqrt(), -0.0);
+        assert_eq!(0.0f32.sqrt(), 0.0);
+        assert_eq!(1.0f32.sqrt(), 1.0);
+        assert_eq!(INFINITY.sqrt(), INFINITY);
+    }
 }
diff --git a/src/libstd/num/f64.rs b/src/libstd/num/f64.rs
index 6fe9fcad2aa..5a5ca65a36d 100644
--- a/src/libstd/num/f64.rs
+++ b/src/libstd/num/f64.rs
@@ -789,4 +789,15 @@ mod tests {
         assert_eq!(NEG_INFINITY.integer_decode(), (4503599627370496, 972, -1));
         assert_eq!(NAN.integer_decode(), (6755399441055744u64, 972i16, 1i8));
     }
+
+    #[test]
+    fn test_sqrt_domain() {
+        assert!(NAN.sqrt().is_nan());
+        assert!(NEG_INFINITY.sqrt().is_nan());
+        assert!((-1.0f64).sqrt().is_nan());
+        assert_eq!((-0.0f64).sqrt(), -0.0);
+        assert_eq!(0.0f64.sqrt(), 0.0);
+        assert_eq!(1.0f64.sqrt(), 1.0);
+        assert_eq!(INFINITY.sqrt(), INFINITY);
+    }
 }