Interfaces in JavaScript with Sweet.js

javascript-interfaces.sjs

macro if_t {
    case { _ $v } => {        
        letstx $vv = [makeValue(#{$v}.map(unwrapSyntax).join(''), #{here})]
        return #{$vv}
    }
}

macroclass iclass {
    pattern {
        rule { $type:if_t $vn:if_t }
    }
}

macro interface {
    rule { 
        $iname $body:iclass ... 
    } => {
        var $iname = {
            included: function() {
                var validations = [], e;
                $(validations.push({'name': $body$vn, 'type': $body$type});) ...

                for(e in validations) {
                    var check = validations[e];
                    var cname = check['name'], ctype = check['type'];

                    if(this.prototype[cname] !== void(0)) {
                        if(ctype != 'var') {
                            if(typeof(this.prototype[cname]) != ctype) {
                                throw new Error('Class doesn\'t implements '+if_t $iname+' interface');
                            }
                        }
                    } else {
                        throw new Error('Class doesn\'t implements '+if_t $iname+' interface');
                    }
                }
            }
        };
    }
}

interface Test
    var foz
    var baz
    object obj

    function test