TypeScript declaration files in node_modules

Question

I have a project with Webpack and TypeScript 3.2. Recently I added the newest version of Playwright, which brings definition files with type imports (import type {APIRequestContext}) which is a TS 3.8 feature. Code completion is broken but the Playwright tests work fine. So that's ok, I guess. But Webpack also throws errors that look like this:

ERROR in src\frontend\node_modules\@playwright\test\types\test.d.ts
[tsl] ERROR in src\frontend\node_modules\@playwright\test\types\test.d.ts(18,13)
      TS1005: '=' expected.

How can Webpack throw this error? The one test file importing Playwright doesn't have any connection to the Webpack entry point. The Webpack config itself ignores anything in the node_modules folder like this

{
  test: /\.ts$/,
  exclude: /node_modules/,
  use: [
    {
      loader: 'ts-loader',
    }
  ]
}