{
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  "path": "/t/could-collections-hypothetically-store-keys-and-values-inline/24195#post_16",
  "publishedAt": "2026-04-30T17:05:17.000Z",
  "site": "https://internals.rust-lang.org",
  "textContent": "Oh interesting, though I do think this is a somewhat different thing.\n\nThis is not a “small map optimization” where if there are few enough key-value pairs, they get stored in the pointers and other stuff you need on the stack anyway (which is what `compact_str` in Rust and “small string optimizations” in C++ do); rather, it specifically reserves space for some number of key-value pairs on the stack.\n\nReserving space on the stack is a different data type which you’re not precluded from creating by guaranteeing that _when you don’t allocate that space_ everything will be stored on the heap,",
  "title": "Could collections hypothetically store keys and values inline?"
}