Agreed, there's a lot of optimizations you can unlock if you ignore JS misfeatures like modifying Array.prototype. But it's important for compilers to be precis

Agreed, there's a lot of optimizations you can unlock if you ignore JS misfeatures like modifying Array.prototype. But it's important for compilers to be precise about the semantics they implement. I just saw the section about enabling checks for when the assumptions are violated, that's a good thing to have.