Type 'T[K]' does not satisfy the constraint '(...args: any) => any'. [ng] 37 [K in FunctionPropertyNames<T>]: ReturnType<T[K]> extends Promise<any> ? K : never; code example

Example: @angular/fire/angularfire2.d.ts:37:49 - error TS2344: Type 'T[K]' does not satisfy the constraint '(...args: any) => any

{
  //...
  compilerOptions: {
    "skipLibCheck": true,
    //...
  }
}