AST.cs

public abstract class TypeName {

}

private sealed class BuiltInTypeName : TypeName {
    private BuiltInTypeName() {

    }

    public static bool operator ==(BuiltInTypeName a, BuiltInTypeName b) {
        return Object.ReferenceEquals(a, b);
    }

    public static BuiltInTypeName UByteTypeName = new BuiltInTypeName();
    public static BuiltInTypeName SByteTypeName = new BuiltInTypeName();
    public static BuiltInTypeName UShortTypeName = new BuiltInTypeName();
    public static BuiltInTypeName SShortTypeName = new BuiltInTypeName();
    public static BuiltInTypeName UIntTypeName = new BuiltInTypeName();
    public static BuiltInTypeName SIntTypeName = new BuiltInTypeName();
    public static BuiltInTypeName ULongTypeName = new BuiltInTypeName();
    public static BuiltInTypeName SLongTypeName = new BuiltInTypeName();
}

public sealed class QualifiedTypeName : TypeName {
    public IList<string> Segments { get; set; }
}