Yet another simple class proposal

class.js

// Guidelines:
// - Class declarations and object literals should have the same features
// - Keep new features at a minimum (apart from what’s already in the object literal proposal)
// - Don’t obscure the fact that private names are actually name objects.
//   => They can also be imported from somewhere else – a use case that needs to be supported.

// Rules:
// - Use # to denote const-ness
//   Alternative: keyword `const`
// - Use @ to refer to name objects
// - there is no syntactic sugar for `this.`

// Name objects:
// - Rough image for what @foo means: “insert arbitrary identifier here”.
//   - Used for property access and to name methods.
// - foo.@bar is syntactic sugar for foo[bar]
//   - Rationale: immediately obvious that it’s property access
class Being <| Monster {

    // non-function prototype properties are forbidden
    
    // Generate name objects
    private {
        age, health, incAge
    }

    constructor(name, weight, age, health) {
        super.constructor(name);
        this.weight = weight;
        this.@age = age;
        this.@health = health;
    }
   
    /* Sugared:
    constructor(name, this.weight, this.@age, this.@health) {
        super.constructor(name);
    }
    */
    
    getNameObjectForAge() {
        return age;
    }

    // private method
    @incAge() {
        this.@age++;
    }

    // getter
    get strength() {
        // stronger with increasing age...
        return super.strength * this.@age;
    }
}.{
    // class properties
    // (possibility: section static { ... })
    
    #MAX_STRENGTH: 400 // constant
}

//////// Options for the subtyping and expression syntax

//// Subtyping syntax: <|

// declarations
class Being <| Monster { ... }
class Monster { ... }

// expressions
let Monster = Being <| class { ... }
let Monster = class { ... }

//// Subtyping syntax: proto

// declarations
class Being proto Monster { ... }
class Monster { ... }

// expressions
let Monster = Being proto class { ... }
let Monster = class { ... }