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Mofei Zhang
69733c5ad8
---
Three functional changes:
- Instead of visiting all identifier references, explicitly traverse only
function decls/exprs. This avoids bugs like accidentally hoisting inline
references
```js
// input
const x = identity(y);
const y = 2;
// lowered HIR before this PR (simplified)
[0] DeclareContext HoistedConst y$0
[1] LoadContext y$0
[2] StoreLocal Const x$5 = identity([1])
```
- Rely on `isReferencedIdentifier()` instead of manually checking member
properties / assignments, which is error prone
```js
// added fixture hoisting-repro-variable-used-in-assignment
const callbk = () => {
// before this PR, we skip hoisting x because it's part of a declaration
const copy = x;
return copy;
};
const x = 2;
return callbk();
```
- Visit lvalues after rvalues. This allows for recursive self-references (e.g.
factorial)
From the Babel side, this change relies heavily on babel's scope binding
resolution logic. My understanding is:
- Babel guarantees node objects are uniqued (`node1 === node2` <--> node1 and
node2 are the same node in the ast)
- Each binding has exactly one `bindingIdentifier` (`binding.identifier`,
`getBindingIdentifier`, etc) which is identifier node @ its declaration site
```js
// x is a binding identifier
const x = 2;
// foo is a binding identifier
function foo() {
}
// param is a binding identifier
(param) => {...}
// this bar is a binding identifier
let bar;
// but not this bar
bar = 2;
```