Article makes one error that is mostly correct but can trip someone up in corner cases. In section 2.5, article makes the assertion `(the τ e) ≈ (or (check-type e τ) e)`

This may be true in some implementations, but the actual defintion of the `(the)` special operator is that if e is not type τ, the behavior of `(the τ e)` is undefined! Crashing when the type is determined to mismatch is one allowed result, but `the` is also the language's "escape hatch" to permit implementations to improve performance by throwing away runtime type information, at which point abusing types will crash in surprising ways.