Minimal typescript test project

.gitignore

node_modules

file.ts

interface X {
  x?: X
}

const x: X = {}
console.log(x.x.x.x)
console.log(x?.x?.x?.x)

package-lock.json

{
  "requires": true,
  "lockfileVersion": 1,
  "dependencies": {
    "typescript": {
      "version": "3.7.4",
      "resolved": "https://registry.npmjs.org/typescript/-/typescript-3.7.4.tgz",
      "integrity": "sha512-A25xv5XCtarLwXpcDNZzCGvW2D1S3/bACratYBx2sax8PefsFhlYmkQicKHvpYflFS8if4zne5zT5kpJ7pzuvw=="
    }
  }
}

tsconfig.json

{
  "compilerOptions": {
    "target": "es5",
    "strict": true
  }
}