Generation of C# serializer for a = nothing field with a default value fails with an obscure exception

[chwarr]

If I have a C# class that has a nullable field and this field has a default value other than null, serialization fails with a very obscure error.

namespace NullableDefValueBug
{
    using Bond;
    using Bond.IO.Safe;
    using Bond.Protocols;

    [Schema]
    public class NullableWithDefault
    {
        [Id(0)] [Type(typeof(Bond.Tag.nullable<int>))] public int? ni = 100;
    }

    class Program
    {
        static void Main(string[] args)
        {
            var obj = new NullableWithDefault();

            var ser = new Serializer<CompactBinaryWriter<OutputBuffer>>(typeof(NullableWithDefault));
         }
    }
}

The error says "The binary operator NotEqual is not defined for the types 'System.Nullable`1[System.Int32]' and 'System.Int32'." An error more like "A nullable field cannot have a default value other than null" is more expected.

Unhandled Exception: 
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> 
System.InvalidOperationException: The binary operator NotEqual is not defined for the types 'System.Nullable`1[System.Int32]' and 
'System.Int32'.
   at System.Linq.Expressions.Expression.GetEqualityComparisonOperator(ExpressionType binaryType, String opName, Expression left, Expression 
right, Boolean liftToNull)
   at System.Linq.Expressions.Expression.NotEqual(Expression left, Expression right, Boolean liftToNull, MethodInfo method)
   at Bond.Expressions.ObjectParser.Field(ITransform transform, Expression structVar, UInt16 id, ISchemaField schemaField, IField field) in 
S:\bondlab\nuget\bond\cs\src\core\expressions\ObjectParser.cs:line 136
   at Bond.Expressions.ObjectParser.<>c__DisplayClass21_0.<Apply>b__4(<>f__AnonymousType0`2 <>h__TransparentIdentifier0, IField knownField) 
in S:\bondlab\nuget\bond\cs\src\core\expressions\ObjectParser.cs:line 88
   at System.Linq.Enumerable.<SelectManyIterator>d__22`3.MoveNext()
   at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection)
   at Bond.Expressions.ObjectParser.Apply(ITransform transform) in S:\bondlab\nuget\bond\cs\src\core\expressions\ObjectParser.cs:line 84
   at Bond.Expressions.SerializerTransform`2.Struct(IParser parser, RuntimeSchema schema, Boolean isBase) in 
S:\bondlab\nuget\bond\cs\src\core\expressions\SerializerTransform.cs:line 173
   at Bond.Expressions.SerializerTransform`2.Struct(IParser parser, RuntimeSchema schema) in 
S:\bondlab\nuget\bond\cs\src\core\expressions\SerializerTransform.cs:line 165
   at Bond.Expressions.SerializerTransform`2.<>c__DisplayClass12_0.<GenerateSerialize>b__0(IParser p) in 
S:\bondlab\nuget\bond\cs\src\core\expressions\SerializerTransform.cs:line 146
   at Bond.Expressions.SerializerGenerator`2.GenerateSerialize(Serialize serialize, IParser parser, ParameterExpression writer, Boolean 
inline) in S:\bondlab\nuget\bond\cs\src\core\expressions\SerializerTransform.cs:line 77
   at Bond.Expressions.SerializerTransform`2.GenerateSerialize(SerializeWithSchema serializeWithSchema, IParser parser, RuntimeSchema 
schema) in S:\bondlab\nuget\bond\cs\src\core\expressions\SerializerTransform.cs:line 155
   at Bond.Expressions.SerializerTransform`2.Generate(IParser parser) in 
S:\bondlab\nuget\bond\cs\src\core\expressions\SerializerTransform.cs:line 125
   at Bond.Serializer`1.SerializerHelper..ctor(ObjectParser parser, Type type, Boolean inlineNested) in 
S:\bondlab\nuget\bond\cs\src\core\Serializer.cs:line 140
   at Bond.Serializer`1.TwoPassSerializerHelper`1..ctor(ObjectParser parser, Type type, Boolean inlineNested) in 
S:\bondlab\nuget\bond\cs\src\core\Serializer.cs:line 0
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] 
activationAttributes, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] 
activationAttributes)
   at System.Activator.CreateInstance(Type type, Object[] args)
   at Bond.Serializer`1..ctor(Type type, IParser parser, Boolean inlineNested) in S:\bondlab\nuget\bond\cs\src\core\Serializer.cs:line 117
   at Bond.Serializer`1..ctor(Type type) in S:\bondlab\nuget\bond\cs\src\core\Serializer.cs:line 91
   at NullableDefValueBug.Program.Main(String[] args) in C:\Users\chwarr\documents\visual studio 
2015\Projects\Playground\CsPlayground\Program.cs:line 19