Throw if CTOR without new

[zbraniecki]

I believe we should be throwing if constructor called without new.

[zbraniecki]

@caridy ?

[littledan]

What's the motivation for this? IIRC @thetalecrafter suggested the opposite at some point.

[vanwagonet]

Throwing without new is the current behavior for Map, Set, and user-defined classes. Personally, I really dislike this behavior, but admit I have no concrete argument against it in general.

Intl.{Collator,DateTimeFormat,NumberFormat} construct a new instance even without new, much like Array or Error. I think consistency with other Intl.* constructors would be good, and changing them to throw without new is probably a web-breaking change. (At least I've written a fair amount of code that use Intl without new.)

[zbraniecki]

Hah, I'm the total opposite, so yeah, it's a matter of preference.

I love the Map and Set behavior and believe that @caridy wanted us to follow that for all new classes. That's why we aimed for this in PluralRules and all future formatters.

[vanwagonet]

Preferences aside, it's probably a lot safer to start with throwing if called without new. If we decide there is a great use for calling as a function later, it's more likely to be web compatible than trying the other way.

[vanwagonet]

It also allows a polyfill to define it with a class.

[littledan]

Being consistent with classes was a big piece of motivation for throwing for other new objects in ES, so it makes sense to apply that here.

[caridy]

@zbraniecki don't commit the generated HTML, that makes the review more difficult, and more conflict-prompt anyways. we can generate the HTML from time to time.

[littledan]

@caridy For repositories I maintain, I regenerate the HTML on each commit. This makes it easier for me and others to see the most recently rendered version. I check in the HTML into the gh-pages branch of the same repository, so it doesn't mess up the history of any other branch and so it's automatically on GitHub pages.

I believe @bterlson has a nice setup where Travis-CI does this build for him. I haven't taken the time to set that up for my repos yet; maybe it would be a nice thing to document in @ljharb's repository template eventually.