this post was submitted on 26 Jun 2024
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Rust Container Cheat Sheet (programming.dev)
submitted 4 months ago by [email protected] to c/[email protected]
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Found this on Mastodon https://fosstodon.org/@dpom/112681955888465502 , and it is a very nice overview of the containers and their layout.

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[–] [email protected] 10 points 4 months ago (2 children)

Nice sheet, though I have a few critiques:

  1. Why does it say where T: Sized for references &T? A reference can definitely point to an unsized type, e.g. &str.
  2. The yellow boxes really mean "must be heap allocated" - all the other references (&T, &[T] and &dyn Trait) may either point to the stack or the heap.
[–] [email protected] 6 points 4 months ago* (last edited 4 months ago)
  1. Why does it say where T: Sized for references &T? A reference can definitely point to an unsized type, e.g. &str.

I think the point being made is that the layout shown only applies for Sized T. Layouts for &[T] and &dyn Trait are shown elsewhere on the sheet. &str is noted under &[T].

Edit: although, similar considerations would apply to other pointer types, but that isn't noted on the sheet except for Box<[T]>

[–] [email protected] 4 points 4 months ago

Because when T is !Sized, the layout is different, it looks more like the layout of &[T].