Fix the sgen issue when use NaN as the default value. (#23366)

* Fix the codegen issue when use NaN as the default value. Move the NaN test from runtimeonly to XmlTest so it will be included in Sgen test run.

* Add brackets.

src/Microsoft.XmlSerializer.Generator/src/Microsoft/XmlSerializer/Generator/XmlSerializationWriter.cs

@@ -2044,7 +2044,16 @@ private void WriteValue(object value)
                 else if (type == typeof(Int32))
                     Writer.Write(((Int32)value).ToString(null, NumberFormatInfo.InvariantInfo));
                 else if (type == typeof(Double))
-                    Writer.Write(((Double)value).ToString("R", NumberFormatInfo.InvariantInfo));
+                {
+                    if (double.IsNaN((Double)value))
+                    {
+                        Writer.Write("double.NaN");
+                    }
+                    else
+                    {
+                        Writer.Write(((Double)value).ToString("R", NumberFormatInfo.InvariantInfo));
+                    }
+                }
                 else if (type == typeof(Boolean))
                     Writer.Write((bool)value ? "true" : "false");
                 else if ((type == typeof(Int16)) || (type == typeof(Int64)) || (type == typeof(UInt16)) || (type == typeof(UInt32)) || (type == typeof(UInt64)) || (type == typeof(Byte)) || (type == typeof(SByte)))
@@ -2058,8 +2067,15 @@ private void WriteValue(object value)
                 }
                 else if (type == typeof(Single))
                 {
-                    Writer.Write(((Single)value).ToString("R", NumberFormatInfo.InvariantInfo));
-                    Writer.Write("f");
+                    if (Single.IsNaN((Single)value))
+                    {
+                        Writer.Write("System.Single.NaN");
+                    }
+                    else
+                    {
+                        Writer.Write(((Single)value).ToString("R", NumberFormatInfo.InvariantInfo));
+                        Writer.Write("f");
+                    }
                 }
                 else if (type == typeof(Decimal))
                 {

src/System.Private.Xml/tests/XmlSerializer/XmlSerializerTests.RuntimeOnly.cs

@@ -2036,22 +2036,6 @@ public static void XmlMembersMapping_CompositeType()
         Assert.Equal(requestBodyValue.composite.StringValue, requestBodyActual.composite.StringValue);
     }
 
-    [Fact]
-    public static void Xml_DefaultValueAttributeSetToNaNTest()
-    {
-        var value = new DefaultValuesSetToNaN();
-        var actual = SerializeAndDeserialize(value,
-@"<?xml version=""1.0""?>
-<DefaultValuesSetToNaN xmlns:xsd=""http://www.w3.org/2001/XMLSchema"" xmlns:xsi=""http://www.w3.org/2001/XMLSchema-instance"">
-  <DoubleField>0</DoubleField>
-  <SingleField>0</SingleField>
-  <DoubleProp>0</DoubleProp>
-  <FloatProp>0</FloatProp>
-</DefaultValuesSetToNaN>");
-        Assert.NotNull(actual);
-        Assert.Equal(value, actual);
-    }
-
     [Fact]
     public static void XmlMembersMapping_SimpleType_HasWrapperElement()
     {

src/System.Private.Xml/tests/XmlSerializer/XmlSerializerTests.cs

@@ -1612,6 +1612,22 @@ public static void Xml_Soap_TypeWithMyCollectionField()
         Assert.True(value.Collection.SequenceEqual(actual.Collection));
     }
 
+    [Fact]
+    public static void Xml_DefaultValueAttributeSetToNaNTest()
+    {
+        var value = new DefaultValuesSetToNaN();
+        var actual = SerializeAndDeserialize(value,
+@"<?xml version=""1.0""?>
+<DefaultValuesSetToNaN xmlns:xsd=""http://www.w3.org/2001/XMLSchema"" xmlns:xsi=""http://www.w3.org/2001/XMLSchema-instance"">
+  <DoubleField>0</DoubleField>
+  <SingleField>0</SingleField>
+  <DoubleProp>0</DoubleProp>
+  <FloatProp>0</FloatProp>
+</DefaultValuesSetToNaN>");
+        Assert.NotNull(actual);
+        Assert.Equal(value, actual);
+    }
+
     private static readonly string s_defaultNs = "http://tempuri.org/";
     private static T RoundTripWithXmlMembersMapping<T>(object requestBodyValue, string memberName, string baseline, bool skipStringCompare = false, string wrapperName = null)
     {

src/System.Runtime.Serialization.Xml/tests/SerializationTypes.RuntimeOnly.cs

@@ -3553,35 +3553,6 @@ public void GetObjectData(SerializationInfo info, StreamingContext context)
     }
 }
 
-public class DefaultValuesSetToNaN
-{
-    [DefaultValue(double.NaN)]
-    public double DoubleProp { get; set; }
-
-    [DefaultValue(float.NaN)]
-    public float FloatProp { get; set; }
-
-    [DefaultValue(Double.NaN)]
-    public Double DoubleField;
-
-    [DefaultValue(Single.NaN)]
-    public Single SingleField;
-
-    public override bool Equals(object obj)
-    {
-        var other = obj as DefaultValuesSetToNaN;
-        return other == null ? false :
-            other.DoubleProp == this.DoubleProp && other.FloatProp == this.FloatProp &&
-            other.DoubleField == this.DoubleField && other.SingleField == this.SingleField;
-    }
-
-    public override int GetHashCode()
-    {
-        return this.DoubleProp.GetHashCode() ^ this.FloatProp.GetHashCode() ^
-            this.DoubleField.GetHashCode() ^ this.SingleField.GetHashCode();
-    }
-}
-
 public class JsonTypes
 {
     public Dictionary<string, string> StringKeyValue

src/System.Runtime.Serialization.Xml/tests/SerializationTypes.cs

@@ -1134,4 +1134,33 @@ public class TypeWithVirtualGenericProperty<T>
 public class TypeWithVirtualGenericPropertyDerived<T> : TypeWithVirtualGenericProperty<T>
 {
     public override T Value { get; set; }
+}
+
+public class DefaultValuesSetToNaN
+{
+    [DefaultValue(double.NaN)]
+    public double DoubleProp { get; set; }
+
+    [DefaultValue(float.NaN)]
+    public float FloatProp { get; set; }
+
+    [DefaultValue(Double.NaN)]
+    public Double DoubleField;
+
+    [DefaultValue(Single.NaN)]
+    public Single SingleField;
+
+    public override bool Equals(object obj)
+    {
+        var other = obj as DefaultValuesSetToNaN;
+        return other == null ? false :
+            other.DoubleProp == this.DoubleProp && other.FloatProp == this.FloatProp &&
+            other.DoubleField == this.DoubleField && other.SingleField == this.SingleField;
+    }
+
+    public override int GetHashCode()
+    {
+        return this.DoubleProp.GetHashCode() ^ this.FloatProp.GetHashCode() ^
+            this.DoubleField.GetHashCode() ^ this.SingleField.GetHashCode();
+    }
 }