Handle NaN in value comparers for double/float

src/EFCore.Relational/Storage/DoubleTypeMapping.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Data;
 using System.Globalization;
+using Microsoft.EntityFrameworkCore.ChangeTracking;
 using JetBrains.Annotations;
 
 namespace Microsoft.EntityFrameworkCore.Storage
@@ -27,7 +28,10 @@ public class DoubleTypeMapping : RelationalTypeMapping
         public DoubleTypeMapping(
             [NotNull] string storeType,
             DbType? dbType = null)
-            : base(storeType, typeof(double), dbType)
+            : base(
+                new RelationalTypeMappingParameters(
+                    new CoreTypeMappingParameters(typeof(double), comparer: new DoubleValueComparer()),
+                    storeType, StoreTypePostfix.None, dbType, unicode: false, size: null, fixedLength: false, precision: null, scale: null))
         {
         }
 

src/EFCore.Relational/Storage/FloatTypeMapping.cs

@@ -5,6 +5,7 @@
 using System.Data;
 using System.Globalization;
 using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.ChangeTracking;
 
 namespace Microsoft.EntityFrameworkCore.Storage
 {
@@ -27,7 +28,10 @@ public class FloatTypeMapping : RelationalTypeMapping
         public FloatTypeMapping(
             [NotNull] string storeType,
             DbType? dbType = null)
-            : base(storeType, typeof(float), dbType)
+            : base(
+                new RelationalTypeMappingParameters(
+                    new CoreTypeMappingParameters(typeof(float), comparer: new FloatValueComparer()),
+                    storeType, StoreTypePostfix.None, dbType, unicode: false, size: null, fixedLength: false, precision: null, scale: null))
         {
         }
 

src/EFCore/ChangeTracking/ArrayStructuralComparer.cs

@@ -7,8 +7,8 @@ namespace Microsoft.EntityFrameworkCore.ChangeTracking
 {
     /// <summary>
     ///     <para>
-    ///         Specifies value snapshotting and comparison for arrays where each element is compared
-    ///         a new array is constructed when snapshotting.
+    ///         Specifies value comparison for arrays where each element pair is compared.
+    ///         A new array is constructed when snapshotting.
     ///     </para>
     /// </summary>
     /// <typeparam name="TElement"> The array element type. </typeparam>

src/EFCore/ChangeTracking/DoubleValueComparer.cs

@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Linq.Expressions;
+using JetBrains.Annotations;
+
+namespace Microsoft.EntityFrameworkCore.ChangeTracking
+{
+    /// <summary>
+    ///     Defines value comparison for <see cref="double" /> which correctly takes <see cref="double.NaN" />
+    ///     into account.
+    /// </summary>
+    public class DoubleValueComparer : ValueComparer<double>
+    {
+        /// <summary>
+        ///     Initializes a new instance of the <see cref="DoubleValueComparer" /> class.
+        /// </summary>
+        public DoubleValueComparer() : base(
+            (x, y) => double.IsNaN(x) ? double.IsNaN(y) : x.Equals(y),
+            d => d.GetHashCode())
+        {
+        }
+    }
+}

src/EFCore/ChangeTracking/FloatValueComparer.cs

@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Linq.Expressions;
+using JetBrains.Annotations;
+
+namespace Microsoft.EntityFrameworkCore.ChangeTracking
+{
+    /// <summary>
+    ///     Defines value comparison for <see cref="float" /> which correctly takes <see cref="float.NaN" />
+    ///     into account.
+    /// </summary>
+    public class FloatValueComparer : ValueComparer<float>
+    {
+        /// <summary>
+        ///     Initializes a new instance of the <see cref="FloatValueComparer" /> class.
+        /// </summary>
+        public FloatValueComparer() : base(
+            (x, y) => float.IsNaN(x) ? float.IsNaN(y) : x.Equals(y),
+            d => d.GetHashCode())
+        {
+        }
+    }
+}

test/EFCore.Relational.Tests/Storage/RelationalTypeMappingTest.cs

@@ -529,6 +529,26 @@ public virtual void UShort_literal_generated_correctly()
             Test_GenerateSqlLiteral_helper(typeMapping, ushort.MaxValue, "65535");
         }
 
+        [ConditionalFact]
+        public virtual void Double_value_comparer_handles_NaN()
+        {
+            var typeMapping = new DoubleTypeMapping("double precision", DbType.Double);
+
+            Assert.True(typeMapping.Comparer.Equals(3.0, 3.0));
+            Assert.True(typeMapping.Comparer.Equals(double.NaN, double.NaN));
+            Assert.False(typeMapping.Comparer.Equals(3.0, double.NaN));
+        }
+
+        [ConditionalFact]
+        public virtual void Float_value_comparer_handles_NaN()
+        {
+            var typeMapping = new FloatTypeMapping("float", DbType.Single);
+
+            Assert.True(typeMapping.Comparer.Equals(3.0f, 3.0f));
+            Assert.True(typeMapping.Comparer.Equals(float.NaN, float.NaN));
+            Assert.False(typeMapping.Comparer.Equals(3.0f, float.NaN));
+        }
+
         [ConditionalFact]
         public virtual void Primary_key_type_mapping_is_picked_up_by_FK_without_going_through_store_type()
         {