**Description:**
And optimize the following situation
```js
export function genElement(el, state) {
if ('slot' === el.tag) return el1 = el, genChildren(el1);
if (el.component) {
var el1
return 999;
}
}
```
which rarely happens in hand written JS, but is often generated by swc merge variable pass.
**Description:**
This PR improves the alias analyzer by distinguishing call and reference, thus reducing the number of identifiers.
---
Co-authored-by: Justin Ridgewell <justin@ridgewell.name>
**Description:**
As we are not using the return value of the function, we can call `ignore_return_value` on the argument of the return statements of IIFE.
**Description:**
This PR renames `CloningMultiReplacer` to `Finalizer` and makes it handle the removal of unused variables. Also, this PR improves the sequential inliner so we can drop variables within a single pass.
**Description:**
We had two passes for joining variables. This PR removes one in the full optimizer, which is wrong.
**Related issue:**
- Closes https://github.com/swc-project/swc/issues/5989.
