- We don't need a list of bindings to check if an identifier is unresolved.
- Checking if an identifier is unresolved is now one CPU instruction.
- Previously it was one hashmap operation.
- This PR also improves performance, by removing the hashmaps mentioned above.
- We now remap parameters using a new syntax context. This is required because we may copy functions, and it can result in duplicated variables with respect to the span hygiene.
- We now visit the sequence expression generated by inlining. This is to improve performance in some cases.
- We now remove variables from variable statements if it's identical to a parameter declared in the function.
- IIFE evaluation is now aware of `this` being different for member expressions.
- We now have more logic for detecting simple functions.
