Symbol polyfill overwrites native Symbol type in typed.js

[tjaneczko]

The polyfill for Symbol (https://github.com/typed-immutable/typed-immutable/blob/master/src/typed.js#L3) always overwrites the native Symbol type since the var declaration is hoisted outside of the if statement, so that polyfill actually will act as the following:

var Symbol
if (typeof(Symbol) === 'undefined') {
  Symbol = hint => `@@${hint}`
  Symbol.for = Symbol
}

This means that you cannot use Symbol as a type, i.e. Map(Symbol, String) will fail.