Handle negative zero

Author: tannergooding

src/libraries/System.Runtime.InteropServices/tests/System.Runtime.InteropServices.UnitTests/System/Runtime/InteropServices/NFloatTests.cs

@@ -2505,7 +2505,7 @@ public static void TanPiTest64(double value, double expectedResult, double allow
         public static void LerpTest32(float value1, float value2, float amount, float expectedResult)
         {
             AssertExtensions.Equal(+expectedResult, (float)NFloat.Lerp(+value1, +value2, amount), 0);
-            AssertExtensions.Equal(-expectedResult, (float)NFloat.Lerp(-value1, -value2, amount), 0);
+            AssertExtensions.Equal((expectedResult == 0.0f) ? expectedResult : -expectedResult, (float)NFloat.Lerp(-value1, -value2, amount), 0);
         }
 
         [ConditionalTheory(typeof(PlatformDetection), nameof(PlatformDetection.Is64BitProcess))]
@@ -2543,7 +2543,7 @@ public static void LerpTest32(float value1, float value2, float amount, float ex
         public static void LerpTest64(double value1, double value2, double amount, double expectedResult)
         {
             AssertExtensions.Equal(+expectedResult, NFloat.Lerp((NFloat)(+value1), (NFloat)(+value2), (NFloat)(amount)), 0);
-            AssertExtensions.Equal(-expectedResult, NFloat.Lerp((NFloat)(-value1), (NFloat)(-value2), (NFloat)(amount)), 0);
+            AssertExtensions.Equal((expectedResult == 0.0) ? expectedResult : -expectedResult, NFloat.Lerp((NFloat)(-value1), (NFloat)(-value2), (NFloat)(amount)), 0);
         }
     }
 }

src/libraries/System.Runtime/tests/System/DoubleTests.cs

@@ -1653,7 +1653,7 @@ public static void TanPiTest(double value, double expectedResult, double allowed
         public static void LerpTest(double value1, double value2, double amount, double expectedResult)
         {
             AssertExtensions.Equal(+expectedResult, double.Lerp(+value1, +value2, amount), 0);
-            AssertExtensions.Equal(-expectedResult, double.Lerp(-value1, -value2, amount), 0);
+            AssertExtensions.Equal((expectedResult == 0.0) ? expectedResult : -expectedResult, double.Lerp(-value1, -value2, amount), 0);
         }
     }
 }

src/libraries/System.Runtime/tests/System/HalfTests.cs

@@ -2116,7 +2116,7 @@ public static IEnumerable<object[]> Lerp_TestData()
         public static void LerpTest(Half value1, Half value2, Half amount, Half expectedResult)
         {
             AssertExtensions.Equal(+expectedResult, Half.Lerp(+value1, +value2, amount), Half.Zero);
-            AssertExtensions.Equal(-expectedResult, Half.Lerp(-value1, -value2, amount), Half.Zero);
+            AssertExtensions.Equal((expectedResult == Half.Zero) ? expectedResult : -expectedResult, Half.Lerp(-value1, -value2, amount), Half.Zero);
         }
     }
 }

src/libraries/System.Runtime/tests/System/SingleTests.cs

@@ -1566,7 +1566,7 @@ public static void TanPiTest(float value, float expectedResult, float allowedVar
         public static void LerpTest(float value1, float value2, float amount, float expectedResult)
         {
             AssertExtensions.Equal(+expectedResult, float.Lerp(+value1, +value2, amount), 0);
-            AssertExtensions.Equal(-expectedResult, float.Lerp(-value1, -value2, amount), 0);
+            AssertExtensions.Equal((expectedResult == 0.0f) ? expectedResult : -expectedResult, float.Lerp(-value1, -value2, amount), 0);
         }
     }
 }