TypeError: b is undefined in __extends


class B extends A {
    constructor(msg:string) { 
        super(msg);
    }
}

class A {
    constructor(public msg:string) {

    }
}

If the super class of B is defined after A you'll get a runtime error.

Just tested the above code in the typescript playground and I get the same error

This issue has been discussed in #21 and has been closed for some bigger issue. this has been a reoccurring pain though.

The consensuses in #21 is to show a compiler error about what the wrong order. we should be able to do this easily using checker.ts::isDefinedBefore.

Add testcase for #4341

Reports error if class declaration appears before extended type decla…

Why isn't this expected behavior?

class B extends A {
    constructor(msg:string) { 
        super(msg);
    }
}
class A {
    constructor(public msg:string) {

    }
}

Generates

var __extends = ... we've all seen this! :) 
var B = (function (_super) {
    __extends(B, _super);
    function B(msg) {
        _super.call(this, msg);
    }
    return B;
})(A);
var A = (function () {
    function A(msg) {
        this.msg = msg;
    }
    return A;
})();

The IIFE after var B = has a parameter of A, but var A = ...isn't called until just after that.

I don't know how you could get the above functionality ... maybe:

var B;
var A;
(function(){
    function b(_super) {
        __extends(B, _super);
        function B(msg) {
            _super.call(this, msg);
        }
        return B;
    }
    function a(){ ... }
    B = b(a);
    A = a;
})()

It's expected, it's just that the compiler should warn you that this will happen.

As mentioned, dupe of #2854

Sheetal Nandi (@sheetalkamat)

Sheetal Nandi (@sheetalkamat) has a fix for the class issue since it has been biting users quite frequently.

I am having the same issue even if the class is used after the other:

BaseClass.ts:

module MyModule {
  class Base {
    constructor() { }
  }
}

ChildClass.ts:

module MyModule {
  class Child extends Base {
    constructor() { super(); }
  }
}

Generates:

/****************************************************************************
  Generated by T4TS.tt - don't make any changes in this file
****************************************************************************/
var __extends = (this && this.__extends) || function (d, b) {
    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
    function __() { this.constructor = d; }
    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};
var MyModule;
(function (MyModule) {
  /** Generated from MyModule.Base **/
  var Base = (function () {
    function Base () {
    }
    return Base;
  })();
  MyModule.Base = Base;
})(MyModule || (MyModule = {}));
var MyModule;
(function (MyModule) {
  /** Generated from MyModule.Child **/
  var Child = (function (_super) {
      __extends(Child, _super);
      function Child() {
          _super.apply(this, arguments);
      }
      return Child;
  })(MyModule.Base);
  MyModule.Child = Child;
})(MyModule|| (MyModule = {}));

It seems that the order is correct, although it doesn't look like it is working as expected.

Rodrigo G. de Queiroz (@rodrigogq)

Rodrigo G. de Queiroz (@rodrigogq) the generated code you posted runs without error. The input code you posted has a compile error because Base is not exported from its module and is thus invisible in the second declaration.

closing in favor of #5207

Fixing issues with TS generation

TypeScript generation fixes (#1047)

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TypeError: b is undefined in __extends #4341

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TypeError: b is undefined in __extends #4341

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mhegazy commented on Aug 17, 2015

nbellowe commented on Aug 20, 2015

DanielRosenwasser commented on Aug 20, 2015

danquirk commented on Aug 20, 2015

mhegazy commented on Aug 20, 2015

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rodrigogq commented on Dec 14, 2015

RyanCavanaugh commented on Dec 14, 2015

mhegazy commented on Feb 22, 2016

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