My original programming language, Expresso -- Tools are now ready

Hi, this is HAZAMA. And this is another blog entry for Expresso.

So far, you can only call methods in some types such as System.Math, but now programs can construct a new instance of a C#'s type, read properties, and resolve which overloads of a method or constructor to call, so we can see .NET Framework as the standard library for Expresso, which will be a big step forward for it. I also introduced the null literal in order to interact with the .NET Framework. I'm planning to prohibit the use of null literals in contexts without .NET. If you need null in other contexts, you can use the Option type in the standard library(I have no idea of how it and other types in the standard library will be provided).

module main;

import "System.IO.File" as File;
import "System.IO.FileStream" as FileStream;
import "System.Text.UTF8Encoding" as UTF8Encoding;


def main()
{
    var writer (- FileStream;
    try{
        writer = File.OpenWrite("./some_text.txt");
        let bytes = UTF8Encoding{encoderShouldEmitUTF8Identifier: true}.GetBytes("This is to test writing a file");
        writer.Write(bytes, 0, bytes.Length);
    }
    finally{
        if writer != null {
            writer.Dispose();
        }
    }
}

The code above comes from the test codes and as you can see, now you can use .NET Framework as if it would be built into Expresso. You can call a constructor by passing values in the order in which the parameters are defined. The compiler is ignoring the names of the arguments because it simply checks that the types of arguments match to the types of parameters of constructors and methods, but I suppose it would be better to check that the types and names of arguments match to those of parameters of constructors and methods(In the code above I used the names of the parameters for those of the fields of the object creation expression). Note that when you call a constructor of an Expresso's type, you have to pass values in the order that the fields are defined in the class definition. Even though you specify the names of the fields, they will be simply ignored. If you need constructors that initialize a new instance with certain values, you can define factory functions that always pass the same values for the fields that you need to have. Note also that you can't define methods in class definitions that return or take themselves as the parameters(so you will define the factory functions in modules).
As you can see, because Expresso doesn't have the using statement as in C#, the body looks ugly. Maybe I should add a similar construct. In addition, I'm planning to make it so that immutable variables won't allow mutating methods to be called as in Rust(In the code above, writer.write will be affected). And because Expresso doesn't have enums, you also can't write code that uses .NET's enums. I'm going to make Expresso's enums algebraic data types, so you won't likely to use C#'s enums directly, but maybe I'll think something out because otherwise you can't write code that uses full capability of the FileStream class. Finally, I converted the names of C#'s methods to camel case. So be careful not to call them like File.OpenFile("./some_text.txt").(Apr. 8 2018 added: This feature has been removed because it makes the language too complex)