Should we have an immutable Range?

[samreid]

From https://github.com/phetsims/totality/issues/221 I wanted to specify an immutable range for the wavelength of light

[samreid]

This was more involved that I hoped, so I will put in a branch for future consideration.

[samreid]

On slack I asked @jessegreenberg if this was worth the complexity, and he replied:

I can't decide - it seems like a lot just for QWI but might be useful generally.

I am wondering if introducing MutableRange and making Range the immutable one by default would be easier. It seems like the large majority of our Ranges are not meant to be mutable.

[samreid]

I asked @jonathanolson and he seemed in favor of adding this to dot, including

Things extending ReadOnlyRange seems good

and he went on to add:

each Range could store whether it is mutable, and we could add checks in places if it should be immutable (though most ranges are created mutably right now)

I'm looking for a system where mutability is a type-checking-time concern.

[samreid]

I feel it is a good idea, but I don't have time to bring it to production at the moment (a couple of hours?). I'll put on dev meeting and we can see if it's important.