Fun with advanced TypeScript

so so i'm always look on the hunt  for how to make uh my static analysis   stricter and in 4.1 there's a new option  which gives me the opportunity to make things   even more strict but it's quite a challenging  rule so let me show you so let me start and   write an array so let's say one two three four  five so far so good and then i can do b equals   a at index zero right maybe  i do so what is the type of b so the type of b should be number i guess  yes perfect or let m...