`TS2354 This syntax requires an imported helper but module 'tslib' cannot be found.`

I see that the code has some references to tslib and importHelpers so I assume this should work transparently. If not, I’ll be happy to know what is missing.

Here is how to reproduce:

Installed packages:

$ npm ls --depth=0
├── resolve@1.3.2
├── rollup@0.41.6
├── rollup-plugin-typescript2@0.4.0
├── tslib@1.6.0
└── typescript@2.2.2

tsconfig.json:

{
    "compilerOptions": {
        "target": "es5"
    }
}

rollup.config.js:

import typescript from 'rollup-plugin-typescript2';

export default {
	entry: './main.ts',

	plugins: [
		typescript()
	]
}

main.ts:

import {Foo} from './module';

console.log("HERE" + Foo);

And module.ts:

export class Foo {}

export class Bar extends Foo {}

When running rollup as follows:

./node_modules/.bin/rollup -c rollup.config.js

I get this error:

🚨   rpt2: module.ts (3,18): semantic error TS2354 This syntax requires an imported helper but module 'tslib' cannot be found.
module.ts

I think this is because the extends syntax requires an __extends helper from tslib, but typescript can’t find tslib.

Expected result is that the required helpers become part of the bundle.

Thanks.

[ezolenko]

Looks like you need "moduleResolution": "node" in tsconfig, otherwise typescript can’t find tslib in node_modules.

Not sure if that could pose problems on non-node setups, but I haven’t heard anything to that effect yet.

[giniedp]

@hueitan i faced the same issue while already having "moduleResolution": "node". Fixed it by adding "tslib": "^1.10.0" to my devDependencies.