Unrelated JSDoc annotation causes class to not be assignable to itself or iterable

[jakebailey]

Bug Report

🔎 Search Terms

jsdoc annotation iterable self assignable

🕗 Version & Regression Information

• This changed between versions 4.2 and 4.3

💻 Code

Here's a compiler repro that reliably works.

// @lib: es2017
// @allowJs: true
// @checkJs: true
// @noEmit: true

// @filename: index.js
const LazySet = require("./LazySet");

/** @type {LazySet<string>} */
const stringSet = new LazySet();

stringSet.addAll(stringSet);


// @filename: LazySet.js
// Comment out this JSDoc, and note that the errors index.js go away.
/**
 * @typedef {Object} SomeObject
 */
void 0;

/**
 * @template T
 */
class LazySet {
    /**
     * @param {Iterable<T>=} iterable
     */
    constructor(iterable) {
        /** @type {Set<T>} */
        this._set = new Set(iterable);
    }

    /**
     * @param {Iterable<T> | LazySet<T>} iterable
     * @returns {LazySet<T>}
     */
    addAll(iterable) {
        return this;
    }

    [Symbol.iterator]() {
        return this._set[Symbol.iterator]();
    }
}

module.exports = LazySet;

🙁 Actual behavior

webpack/webpack#16957 (comment)

Argument of type 'LazySet<string>' is not assignable to parameter of type 'Iterable<string> | LazySet<string>'.
  Property '[Symbol.iterator]' is missing in type 'import("/home/jabaile/work/webpack-repro/lib/LazySet")<string>' but required in type 'import("/home/jabaile/work/webpack-repro/lib/LazySet")<string>'.ts(2345)
LazySet.js(27, 2): '[Symbol.iterator]' is declared here.

Note that LazySet is not assignable to LazySet, which is weird. Changing the signature of addAll to just be Iterable<T> is equivalent.

Also, if you actually construct this example in the editor, editing index.js will make the error go away temporarily, until tsserver is restarted, or LazySet.js is edited. Very odd.

🙂 Expected behavior

No errors.

@alexander-akait @TheLarkInn

[sandersn]

My initial guess is that the implicit export SomeObject turns the single export of LazySet.js into an export of a namespace, but in a non-standard incorrect way that doesn't issue the correct error.

Edit: The fact that the error can go away when rebuilding the checker implies that there may be a missing call to mergeSymbol somewhere in a JS-specific code path.

[sandersn]

Slightly simplified repro (this version only has one call to make debugging easier):

// @lib: es2017
// @allowJs: true
// @checkJs: true
// @noEmit: true
// from #53967, based on webpack/webpack#16957

// @filename: index.js
const LazySet = require("./LazySet");

/** @type {LazySet} */
const stringSet = undefined;
stringSet.addAll(stringSet);


// @filename: LazySet.js
// Comment out this JSDoc, and note that the errors index.js go away.
/**
 * @typedef {Object} SomeObject
 */
class LazySet {
    /**
     * @param {LazySet} iterable
     */
    addAll(iterable) {}
    [Symbol.iterator]() {}
}

module.exports = LazySet;

[regseb]

Maybe I have a similar problem? The type from a JavaScript import is incompatible with a JSDoc import.

Files

• package.json

  {
    "name": "testcase",
    "version": "1.0.0",
    "type": "module",
    "dependencies": {
      "typescript": "5.2.2"
    }
  }

• foo.js

  export default class Foo {}

• index.js

  import FooJs from "./foo.js";
  
  /**
   * @typedef {import("./foo.js")} FooJsDoc
   */
  
  /**
   * @type {FooJsDoc}
   */
  const foo = new FooJs();

To reproduce

1. npm install
2. npx tsc --allowJs --noEmit --checkJs index.js

Actual behavior

index.js:10:7 - error TS2741: Property 'Foo' is missing in type 'Foo' but required in type 'typeof import("/home/regseb/dev/testcase/foo")'.

10 const foo = new FooJs();
         ~~~

  foo.js:1:22
    1 export default class Foo {}
                           ~~~
    'Foo' is declared here.


Found 1 error in index.js:10

---

Edit: #55608

[sandersn]

It could be related because of the @typedef, but you're using ES-standard imports, so it's probably different. I'd recommend filing a bug that references this one.