Hello, maybe someone here knows the history of block-scoped functions.

We have a very old Babel plugin, enabled by default, that does this transform (@babel/plugin-transform-block-scoped-functions):

{ function f() {} }
// --->
{ let f = function f() {} }

This plugin was created in response to this issue: https://github.com/babel/babel/issues/514

Does anyone know:

• why does Babel need to transform functions in blocks? Do they not work in older engines or older ECMAScript versions?
• should the transform use let or var?

Thank you! Follow-up question:

We also have this test, that ensures that the function is hoisted to the outer scope when there is a variable with the same name (but only when we are also compiling let/const to var):

var run = function () {
  return false;
};

if (true) {
  function run() {
    return true;
  }
}

function test() {
  return run();
}

// ---- OUTPUT --->

var run = function () {
  return false;
};
if (true) {
  var run = function () {
    return true;
  };
}
function test() {
  return run();
}

is this annex b behavior?

Thank you!

Another thing we should to in Babel 8 is deciding if we want to consider Annex B or not, instead of enabling it sometimes