I tried to write a snippet that would be detected at compile time, but was unable, apparently due to my PHP engine's interpreted nature. The creator(s) should have provided a usage example (for end-users) or pointed to PHP sources for an example of where/how it's used. None of the provided examples, to date, reflect an exception detected at compile time, as this class asserts.
IMO it's hopeful at best to expect a compiler to detect an illegal index in a dynamically-typed, typically JIT-executed, enviro. Since when is there a strict contract of what indexes should be considered "within range" and how would the compiler know about this contract? Also, how would we try/catch that in the compile phase?
SPL also provides the OutOfBounds exception. If this class, its parent, and OOB have little distinction, then does SPL need all 3?