[turbopack] Treat local `const` assignments as side-effect free (#94294)
This is a follow-up to this comment:
https://github.com/vercel/next.js/blob/89562628d27b672352d212ecd8c6941873e83222/turbopack/crates/turbopack-ecmascript/src/analyzer/side_effects.rs#L22
I wouldn't consider it a comprehensive tracker of local variables.
However, it's a start. Only `const`s are tracked at the moment. This is
because with `let`s you can do things like:
```javascript
let x = { a: "b" };
x = globalThis;
x.a = "b" // side effect!
```
I do think this is a helpful improvement, though as it handles the
common pattern that was mentioned in the comment.
next.js
7e375d00 - [turbopack] Treat local `const` assignments as side-effect free (#94294)
