{
  "$type": "site.standard.document",
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  "path": "/t/implement-fusediterator-for-core-stepby/24074#post_3",
  "publishedAt": "2026-03-12T19:15:47.000Z",
  "site": "https://internals.rust-lang.org",
  "textContent": "philomathic_life:\n\n> Should the correctness of the `impl` be dependent on the correctness of the underlying `Iterator`'s `impl`?\n\nI don't understand why you'd answer that question with \"no\". Did you accidentally write the opposite of what you meant (dependent vs independent)?\n\nThe naive implementation of `StepBy` is only fused if the underlying iterator is fused. If the underlying iterator is incorrectly claiming to be fused, `StepBy`'s claim to be fused would be just as incorrect. Which is completely fine.\n\nAttempting to work around by fusing in `StepBy` would hurt performance, change existing behaviour, and require specialization. So it's clearly not a sane option.",
  "title": "Implement FusedIterator for core::iter::StepBy"
}