TypeScript 4.0 broken on Node.js 6

[DanielRosenwasser]

> volta install node@6
success: installed and set node@6.17.1 (with npm@3.10.10) as default                                                                                                      
> tsc
\tsc.js:5962
    var textToKeyword = new ts.Map(ts.getEntries(textToKeywordObj));
                        ^

TypeError: Iterator value undefined is not an entry object
    at new Map (native)
    at ts (tsc.js:5962:25)
    at Object.<anonymous> (tsc.js:7884:3)
    at Module._compile (module.js:577:32)
    at Object.Module._extensions..js (module.js:586:10)
    at Module.load (module.js:494:32)
    at tryModuleLoad (module.js:453:12)
    at Function.Module._load (module.js:445:3)
    at Module.require (module.js:504:17)
    at require (internal/module.js:20:19)

[RyanCavanaugh]

I didn't think we supported node 6 anymore?

[DanielRosenwasser]

We don't test on it; but it's only 4 years old; we're supposed to work in environments going back to ES5 though.

[sindresorhus]

Node.js 6 is not even supported by the Node.js team: https://github.com/nodejs/Release#end-of-life-releases