This has been proposed before. The current implementation is intentional, as
seen on the swift-evolution repo:
https://github.com/apple/swift-evolution/blob/master/commonly_proposed.md#strings-characters-and-collection-types
<https://github.com/apple/swift-evolution/blob/master/commonly_proposed.md#strings-characters-and-collection-types>.
This is why:
https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20151214/002446.html
> Recently I’ve been considering the lack of safety around array indexes. Swift
> is designed with safety in mind, so this example would not compile:
>
> var myString: String? = “hello”
> myString.append(“ world!”)
>
> The string is optional, not guaranteed to exist, so the last line requires a
> “!” to force-unwrap it.
>
>
>
> public func tableView(_ tableView: UITableView, numberOfRowsInSection
> section: Int) ->Int {
> let section = self.sections[section]
>
> return section.items.count
> }
>
> In this example, we could provide a section number that goes beyond the
> bounds of the self.sections array, without any warning.
>
> My suggestion is perhaps arrays should by default return an optional when
> given an index, and of course they’d support forced-unwrapping too. So you
> could then do this:
>
> let section = self.sections[section]
> if section == nil {
> return 0
> } else {
> return section!.items.count
> }
>
> Or you could do this:
>
> let section = self.sections[section]!
>
> return section.items.count
>
>
>
> Of course this would be less convenient in a lot of cases, but this is the 1
> place where apps seem to encounter a crash, crashing for the same reason
> that’s especially avoided across most of the rest of
> Swift._______________________________________________
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> [email protected]
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>
>
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