[babel 8] Remove methods starting with _ in @babel/traverse

[liuxingbaoyu]

Q	A
Fixed Issues?	Ref: #16443
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/56919

[liuxingbaoyu]

It has a reference externally.

[nicolo-ribaudo]

What do you think of changing all these "private methods" to accept the NodePath as the first parameter instead of this, so that we can do _resyncParent(this) instead of _resyncParent.call(this)?

Then, in index.ts we have to do

Object.assign(NodePath_Final.prototype, {
  ...
  _resyncParent: thisify(NodePath_context._resyncParent)
  ...

where thisify is

function thisify(fn) {
  return function() {
    return fn(this, ...arguments);
  }
}

in practice those thisified functions will never be called anyway, since they are only called internally by @babel/traverse.

[liuxingbaoyu]

Maybe we can do this after Babel 8 is more stable and avoid us needing to expose certain methods.