{
  "$type": "site.standard.document",
  "bskyPostRef": {
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    "uri": "at://did:plc:ivbknywyskln22er3nkssdhl/app.bsky.feed.post/3mhyxlv4plgu2"
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  "path": "/t/on-replacing-unsafecell/24113#post_3",
  "publishedAt": "2026-03-26T17:29:43.000Z",
  "site": "https://internals.rust-lang.org",
  "tags": [
    "Debug defined on the unsafecell"
  ],
  "textContent": "ProgramCrafter:\n\n> structs are now also allowed to have _twilight_ fields which are internally mutable and potentially uninitialized\n\nI'm generally opposed to any feature which makes fields not uphold their usual invariants. If the field is `i32` and you can get an `&i32`, that should be a legal `&i32`, but that doesn't hold here.\n\nThe wrapper type is really useful because getting a `&UnsafeCell<i32>` is perfectly fine -- it can be passed around, it can have Debug defined on the unsafecell so that `derive(Debug)` works, etc.\n\nAttributes that add _extra_ guarantees is fine -- a `&i32` to a field with `#[align(128)]` is still usable, for example -- but removing type things is best done with a wrapper, not an attribute.",
  "title": "On replacing UnsafeCell"
}