I've started digging through the codebase on wins with regards to performance, I've seen a lot of them.... However, some of them also come down to our ... weird usage of TypeScript.

Let's take the Token as an example, we did a great thing in creating it as a class as it enforced consistent monomorphic backing shapes, however we do a non-null assertion, for the reason that value can actually be undefined. When we use Token we always assume that value is defined which makes all of this deopt as we will call functions with string | undefined the whole thing while our code is geared for string.

I've attempted to make value the correct type which resulted in a lot more issues.

In addition to that we have a lot of call-sites for the .slice method, we however do polymorphic access on it as adjacent call-sites will invoke String.slice right next to Array.slice which makes .slice not optimizeable, instead we can resort to converting String.slice into String.substring to avoid this issue all together.

The last noLocation parse bailout remaining is the .slice case of blockstring.ts

The improvements on the parser benchmark are currently minimal, I am trying to discover the deopts and how we can have a way forward.