importHelpers option causes compiler errors

[ckotzbauer]

TypeScript Version: 2.2.1

Environment:

• Windows 10
• Node 7.6.0
• NPM 4.1.2
• TypeScript 2.2.1
• tslib 1.6.0

The recently added compiler option "importHelpers" causes compiler errors. There are several other closed issues where this problem was described: #12724, #12775, #12. This should be fixed, in TS 2.1.5 or 2.2.x but it still occurs.
It's a simple compiler error in the CLI. In vscode (latest version 1.10.1) the "extends" keyword causes the error.

I created a small skeleton which demonstrates this bug: https://github.com/code-chris/tslib-compile-error. This was tested on a windows machine with the specs above.

Expected behavior:
There's no compilation error when "importHelpers" option is enabled.

Actual behavior:
The compilation result is runnable and correct, but there's a compilation error like this:

src/main.ts(5,19): error TS2354: This syntax requires an imported helper but module 'tslib' cannot be found.

[delagen]

I still see this error when use webpack with awesome-typescript-loader in case tslib resolved via webpack

It can't find that module because your module resolution is set to the default, which doesn't look in node_modules. You can fix this by adding "moduleResolution": "node" to your tsconfig.json. We could probably improve the error message here.

[delagen]

Espessialy for Andy (Andrewkraft) (@Andy-MS)
There is no this module in node_modules or anywhere which can be resolved via moduleResolution.
Path to tslib module written in paths setting of tsconfig.json and at bundle resolved via webpack. All works but dianostics message still appear

Sergey Vohmyanin (@delagen) Could you provide a repro for your case? Also try using --traceResolution so see where it looks.

[ckotzbauer]

Andy (Andrewkraft) (@Andy-MS) The moduleResoution fixed the bug in my skeleton from my first post. But yes, the message isn't clear.
Sergey Vohmyanin (@delagen) What do you mean with "no this module"?

[delagen]

Andy (Andrewkraft) (@Andy-MS) https://github.com/Delagen/typescript-issue14468
npm run test -- success

Found 2 issues which not related to webpack or any other. So it's base behavior of TS.
npm run test.fail
When extend another tsconfig.json and have own paths its simply override base config paths section (may be extend?)
npm run test.fail2
When extend another tsconfig.json paths of base config resolved using root baseUrl and not using baseUrl from base config (relative to its path)

code-chris I mean tslib module installed outside generic moduleResolution from base module.

Sergey Vohmyanin (@delagen) I created #14527 for your issue. Assuming it happens for all libraries and not just for tslib.

[delagen]

Work as intended ) - expected answer