Never hoist JSX elts referencing vars from the current scope

[nicolo-ribaudo]

Q	A
Fixed Issues?	Fixes #14363
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

[nicolo-ribaudo]

The old output was

var _Component;

function RoutesComponent() {
  return (
    <Routes>
      {(c) => {
        {
          const Component = c;
          return _Component || (_Component = <Component />);
        }
      }}
    </Routes>
  );
}

[nicolo-ribaudo]

This is now more complex, because in cases like

function f() {
  let Component;
  {
    return <Component />;
  }
}

jsxScope is the block statement while targetScope is the function: we still do not want to hoist the element, because it's unnecessary (there are already 2-3 tests covering this).

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/51873/