Multiple `const mod =` definitions? about deno_emit

[jflatow]

Ok, I believe I tracked this down to an issue with eval, which I know is evil, but still part of the language. I noticed that there can be various issues when bundling code with eval in it, but I've created a minimal example which reproduces the one I am reporting here (multiple mod definitions).

Consider three files: multi-mod.A.ts, multi-mod.B.ts, and multi-mod.importer.ts:

export class A {}

export class B {}

import * as m1 from './multi-mod.A.ts';
import * as m2 from './multi-mod.B.ts';
const { A } = m1;
const { B } = m2;
eval('');

If you bundle the importer script, you get multiple definitions of mod.

If you remove B from the picture you can see a different but related issue that Identifier 'A' has already been declared.

[jflatow]

As a workaround for anyone else running into this issue: you can replace eval with window.eval if the code doesn't need access to local state.

[jflatow]

There's a separate but related bug if you export the name mod in user-space code yourself, the emitted module gets overwritten.