Static decorator check.

gistfile1.txt

function procedure(instance, method, description) {
  
  //console.log(description)
  description.value.__procedure = true;
  var org = description.value;
  if (instance.__procedureDefined) {
    throw new Error('Already has one procedure');
  }
  instance.__procedureDefined = true;
  description.value = function() {
    console.log('>>>>> wrapped');
    return org.apply(this, arguments)
  }
}

class Clz{
  @procedure
  main() {
    console.log('>>>> original');
    return 3;
  }
  //@procedure
  notmain() {
    console.log('<<<< should not happen');
  }
}

var c = new Clz();
c.main();
console.log(c.main.__procedure);