{
  "$type": "site.standard.document",
  "bskyPostRef": {
    "cid": "bafyreies54fa5mbfan6ig7jqvccpudo4ytqgqnp42pfku6xxfug5kpagke",
    "uri": "at://did:plc:ivbknywyskln22er3nkssdhl/app.bsky.feed.post/3mg6mownqaex2"
  },
  "path": "/t/f-pattern-types-subsets-enums-using-as/24048#post_16",
  "publishedAt": "2026-03-03T18:39:04.000Z",
  "site": "https://internals.rust-lang.org",
  "textContent": "scottmcm:\n\n> The hard question is whether `Result<T, MyErrorSubset>` can actually be any smaller if it's defined that way.\n\nIn my opinion, the main benefit to pattern types is in exhaustiveness checking in e.g. `match` constructs and other static guarantees, though it'll be a nice extra if e.g. `Result<NonZeroU32, MyError is MyError::NotFound>` gets optimized to the same size as a `u32`. An initial implementation which handles the language semantics, but leaving open optimization opportunities for later, would be good enough for me to be happy.",
  "title": "F-pattern_types : Subsets enums using as"
}