JS immutable identifier binding

val.js

/*
  A sweet.js macro for adding a JS identifier 
  binding (`val`) that is the same as a `const` declaration, 
  that is then frozen with `Object.freeze`.
*/

'use strict';

macro val {
    rule {
        $Identifier:ident = $Initializer:expr;
    } => {
        const $Identifier = Object.freeze($Initializer);
    }
}


val a = [1,2,3,4];
val b = { test: "yep" };

a.push(5);
>> TypeError: a.push(...) is not extensible

b.test = "nope";
>> TypeError: "test" is read-only

This is a sweet.js macro. Test it out in the editor.