关闭包含构造函数的对象的编译器注释

Question

I'm trying to typecheck a library that returns an Object of constructor functions. With the following code Closure errors with:

./my-app.js:11: ERROR - Cannot call non-function type Foo.Wheel
const wheel = new Foo.Wheel();
               ^

Here's the code structure:

my-app-code.js - The code I'm using

const Foo = /** @type{!Foo.Module} */ require('foo');
const wheel = new Foo.Wheel();
wheel.rotate();

externs-foo.js - Closure externs for the Foo library

/** @const */
const Foo = {};


/** @record */
Foo.Module = function() {};

/** @type {!Foo.Wheel} */
Foo.Module.prototype.Wheel;

/** @constructor */
Foo.Wheel = function() {};

/**
* @returns {void}
*/
Foo.Wheel.prototype.rotate = function() {};

foo/index.js - corresponds to Foo.Module type.

module.exports = {
  Wheel: require("./wheel"),
};

foo/wheel.js - corresponds to Foo.Wheel.

function Wheel() {}

Wheel.prototype.rotate = function() {};

module.exports = Wheel;

I tried one variation on externs-foo.js with the following results.

Make Foo.module.prototype.Wheel a function

/** @return {!Foo.Wheel} */
Foo.Module.prototype.Wheel = function() {};

Errors with:

my-app.js:11: ERROR - Expected a constructor but found type function(this:Foo.Module):Foo.Wheel.
const wheel = new Foo.Wheel();

my-app.js:13: ERROR - Property rotate never defined on module$myapp_Foo of type Foo.Module
wheel.rotate();

Answer 1

I'm aware of two solutions to this issue:

1. Declaring Foo.Module.prototype.Wheel = Foo.Wheel; in the externs file.
2. Use @type {function(new:Foo.Wheel)} , which says that the function is in fact a constructor that instantiates a Foo.Wheel object.

I prefer solution #1 because it declares a reference to the constructor function, so the compiler will allow me to access properties of the constructor (eg static methods). IIRC this can't be done in solution #2.

The annotations @type {!Foo.Wheel} and @return {!Foo.Wheel} won't work because they refer to an instance of Foo.Wheel and what you actually want is the constructor itself.