All of our static evaluation & dead-code elimination transforms need to
happen in post-order, transforming inner nodes first. This is so that
in complex nested cases all transforms see the simplified version of
their inner nodes.
For example:
async getNimbusExperimentData() {
if (!PDFJSDev.test("GECKOVIEW")) { return null; }
// other code
}
-> [evaluation of PDFJSDev.*]
async getNimbusExperimentData() {
if (!false) { return null; }
// other code
}
-> [!false -> true]
async getNimbusExperimentData() {
if (true) { return null; }
// other code
}
-> [if (true) -> replace with the if branch]
async getNimbusExperimentData() {
return null;
// other code
}
-> [early return -> remove dead code]
async getNimbusExperimentData() {
return null;
// other code
}
This was done correctly in all cases except for our `UnaryExpression`
transform, which was happening in pre-order.
