tsconfig-base.json

{
  "compilerOptions": {
    "strict": true,
    "alwaysStrict": true,
    "noImplicitAny": true,
    "noImplicitReturns": true,
    "noImplicitThis": true,
    "noEmitOnError": true,
    "strictNullChecks": true,
    "experimentalDecorators": true,
    "preserveConstEnums": false,
    "downlevelIteration": true
  }
}