Function name cannot be reassigned in it's scope.

[ahaoboy]

Describe the bug
Function name cannot be reassigned in it's scope.

To Reproduce

boa ./main.js

Uncaught TypeError: cannot mutate an immutable binding 'fn'

"use strict";

function fn() {
  fn = function () { }
}


fn()

This is ok.

"use strict";

function fn() {
}


fn = 1;