Recursively `class`-`func` definitions in Motoko.

RecClassFunc.mo

// Recursion via "manual back-patching"
//
// What?
// MyClass is defined recursively with myFunc, which refer to each other.
//
// How?
// The myClass method uses a variable for mutable storage (myClass_) to
// determine if the initialization has occured yet or not.

class Test() {
  type Init = { boom : () -> ()};
  class MyClass(init : Init) {
    let y = init.boom;
    public func bap() {
      y()
    };
  };
  var myClass_ : ?MyClass = null;
  func myFunc(){ myClass().bap() };
  func myClass() : MyClass {
    switch myClass_ {
      case null {
        let x = MyClass({boom = myFunc});
        myClass_ := ?x;
        x
      };
      case (?x) x;
    }
  };
}