Building Angular project error "Duplicate identifier 'IteratorResult'"

Question

I'm trying to build --prod my angular project and it keeps giving me this error

Failed to compile.

node_modules/@types/node/index.d.ts:73:11 - error TS2300: Duplicate identifier 'IteratorResult'.

73 interface IteratorResult<T> { }
             ~~~~~~~~~~~~~~

  node_modules/typescript/lib/lib.es2015.iterable.d.ts:41:6
    41 type IteratorResult<T, TReturn = any> = IteratorYieldResult<T> | IteratorReturnResult<TReturn>;
            ~~~~~~~~~~~~~~
    'IteratorResult' was also declared here.
node_modules/typescript/lib/lib.es2015.iterable.d.ts:41:6 - error TS2300: Duplicate identifier 'IteratorResult'.

41 type IteratorResult<T, TReturn = any> = IteratorYieldResult<T> | IteratorReturnResult<TReturn>;
        ~~~~~~~~~~~~~~

  node_modules/@types/node/index.d.ts:73:11
    73 interface IteratorResult<T> { }
                 ~~~~~~~~~~~~~~
    'IteratorResult' was also declared here.

I tried to install node modules again but I'm still getting this error.

Try npm install --save-dev @types/node and see

skdonthi
– skdonthi

2020-03-08 16:16:20 +00:00
Commented Mar 8, 2020 at 16:16 — skdonthi
– skdonthi, Commented Mar 8, 2020 at 16:16

Aleš Doganoc · Accepted Answer · 2020-03-08 21:44:18Z

2

Add skipLibCheck: true to your tsconfig.json file. This prevents type checking the declaration files so you should not have the issue anymore. Here is also a link to the description in the documentation.

Possibly also upgrading some of the type definitions as suggested in the comment could help maybe you are using very old versions or you have duplicate references.

answered Mar 8, 2020 at 21:44

Aleš Doganoc

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1 Comment

adrianus Over a year ago

I had trouble using Angular WebWorkers with localize and this solved the issue. Thanks!

PEC · Accepted Answer · 2021-01-05 11:08:15Z

1

in my case, I get the TS2300: Duplicate identifier error when compiling my main project for the following reason:

In the my-custom-library.module.ts, I accidentally entered the path of the component causing the error with the wrong case.

import { InputPasswordComponent } from './components/input-Password/input-Password.component';

instead of

import { InputPasswordComponent } from './components/input-password/input-password.component';

This is confusing because no error is thrown while compiling the custom library. (ng build --prod).

Obviously, the skipLibCheck: true solution does not work in this particular case.

answered Jan 5, 2021 at 11:08

PEC

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1 Comment

Pic Mickael Over a year ago

That was my problem too, I messed up the camelcasing in my component template and styleUrls. skipLibCheck is not a solution because it does not fix the problem, it just ignore it. Which can have consequences in the future.

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