Bad type annotation warnings for identifiers from re-exported modules

Given:

// a.js
export default class A {
  constructor() {
    /** @type {string} */
    this.message = 'Hello';
  }
}

// b.js
import A from './a';

export {A};

// c.js
import {A} from './b';

class C {
  /**
   * @param {!A} a
   */
  constructor(a) {
    /** @const */
    this.a = a;
  }
}

console.log(new C(new A()).a.message);

Running:

java -jar path/to/compiler.jar \
--compilation_level ADVANCED \
--js *.js \
--language_out ECMASCRIPT5_STRICT \
--entry_point c.js

Yields:

c.js:5: WARNING - Bad type annotation. Unknown type A$$module$b
   * @param {!A} a
              ^

0 error(s), 1 warning(s), 90.3% typed
'use strict';console.log((new function(a){this.a=a}(new function(){this.message="Hello"})).a.message);

It seems that closure is having some issues with types from re-exported modules from a different file. If I change the initial statement in c.js to import A from './a' the code compiles fine.

p.s. Sorry if this is a dupe; I searched through the current issues but missed anything pertaining to this.

[MatrixFrog]

I suspect the code we’re producing is correct; it just doesn’t typecheck well.

I don’t expect to have time to look at this in the near future but we should definitely fix it. Sometimes when an alias is annotated @const that helps the compiler to understand it’s supposed to be treated as an alias. So the first thing I’d try is running this example with --preserve_type_annotations and see if we have those @const annotations. If not, you can try going into the ProcessEs6Modules class and adding them. See https://github.com/google/closure-compiler/wiki/Writing-Compiler-Pass if you haven’t worked in the compiler code base before.

[ChadKillingsworth]

Also - we most very much want to keep all 3 module systems at parity. Any fix/change needs to apply to all 3.