Safe Random Access Collection Element

[Jens]

This has already been mentioned but I think it's worth repeating: If this failable subscript should ever be added to the stdlib, the label cannot be "safe" or "checked", because that would be misleading and confusing, ie:

@Jens

Both arr[checked:] and arr[safe:] imply that the existing unlabeled subscript is unchecked and unsafe , which is incorrect.

The existing unlabeled subscript is both safe and checked . It is safe (in the sense Swift uses the word) because it checks whether the given index is within bounds and traps otherwise.

An unsafe or unchecked version of the subscript would not do any bounds check (for efficiency I guess) and have undefined behavior for out of bounds indices.

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I have never felt the need for this failable subscript myself, and have no strong opinion on whether it should be added or not.