[Draft] Adding Safe indexing to Array

[bzamayo (Benjamin Mayo)]

I think newcomers to the language will reach for array[checked:] (or whatever it is called) in the same way people misuse postifx ? today, as documented by endless examples elsewhere on the web.

@saagarjha

Well, this code without the guard is obviously fundamentally wrong either way, whether it’s using regular subscripting or safe indexing, since the arrays are of different length.

That's sort of the point of the example. If you guarded at the top of the dummy example I gave with a condition like array2.count == array1.count then you spell out the preconditions early, and can consciously decide the right behaviour.
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