assert and CFA

[kitsonk]

Tracking issue.

After originally indicating it was a design limitation, the TypeScript team revisited allowing the ability to model type narrowing via assert(). The assert() pattern is heavily used within Deno and once microsoft/TypeScript#32695 is landed is part of a TypeScript release we will be able to make all of our code more sound.

[hayd]

Update: This is merged to TS.

[kitsonk]

🎉 then that means it will be part of 3.7. There is a lot of code we will want to update on the back of it!!!

[kitsonk]

Implemented in code base now. Closing.