{
  "$type": "site.standard.document",
  "bskyPostRef": {
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    "uri": "at://did:plc:b3tz6srl4ochk2wxn6dv6xpy/app.bsky.feed.post/3mk3yywdpuuj2"
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  "path": "/Articles/1067220/",
  "publishedAt": "2026-04-22T13:58:35.000Z",
  "site": "https://lwn.net",
  "tags": [
    "RFC 3729"
  ],
  "textContent": "In Rust, types either possess a constant size known at compile time, or a dynamically calculated size known at run time. That is fine for most purposes, but recent proposals for the language have shown the need for a more fine-grained hierarchy. \nRFC 3729 from David Wood and Rémy Rakic would add a hierarchy of traits to describe types with sizes known under different circumstances. While the idea has been subject to discussion for many years, a growing number of use cases for the feature have come to light.",
  "title": "[$] One Sized trait does not fit all"
}