Your class is not syntactically valid ES2015. Typescript is allowing a shorthand that ES2015 doesn't allow and rewrites it to proper ES2015. It's a tiny babel plugin. Maybe a stricter output target should provide a syntax warning here.
The source conversion here, based on the implications of the shorthand, shouldn't be a surprising output and looks like perfectly readable, idiomatic JS to me.
Can you turn of those transpilations though? Readable code isn't the problem, equivalence is. Flow will never rewrite anything, which is what I've been saying.
Many of the transpilations you can turn off. The targets system turns off/on many transpilations as a suite. There are flags for several others such as `--noEmitHelpers`, `--preserveConstEnums`, `--jsx Preserve`.
If you have a reason to disallow and/or preserve something that TS does not already support, I would think the Typescript team would be interested in hearing about it.
But the argument I'm making is it's disingenuous to say that Flow and Typescript are both equally "not Javascript". Flow is _strictly_ additive to whatever else your toolchain is. Typescript is a different language.
I never said that Flow and Typescript are "equally" not JavaScript. I think you are getting your arguments crossed here.
Though I will state that both are not JavaScript, even if they are "unequally" not JS (for whatever that distinction means to you, though I think it is a moot point). Flow when used purely as comments is JS, sure, but the type annotation syntax is not JS as defined by any ES standard (except maybe ES4) nor any JS accepted by browsers (definitely not ES4). "Strictly additive" isn't a distinction that matters to what constitutes a language, if we want to be pedantic.
Finally, I would suggest you refrain from the word "disingenuous". Yes, my opinions differ from your own, but you cannot speak to the candor of my opinions here. I am hoping you did not intend an ad hominem attack, but I don't think a lot of people realize how much "disingenuous" is an ad hominem attack.
The source conversion here, based on the implications of the shorthand, shouldn't be a surprising output and looks like perfectly readable, idiomatic JS to me.