Should most allocators be Clone?

[shlevy]

I'm creating a data structure that includes Boxes and Vecs and Vecs of Boxes, and I find myself between two choices:

1. Have the top-level data structure own the Allocator and have each nested structure use the free &A implementation
2. Require the Allocator to be Clone and just clone it at each usage point

Based on this section in the docs:

cloning or moving the allocator must not invalidate memory blocks returned from this allocator. A cloned allocator must behave like the same allocator

it seems like the expected pattern is 2, and that therefore most allocators will be Clone. Is that correct?

[Amanieu]

hashbrown also requires allocators to be Clone. In practice I would expect the vast majority of allocators to be Clone.

[RustyYato]

Note that you can always create a Clone allocator by using &T. So the Clone bound is strictly more general, as it also allows non-&T allocators.

[cmazakas]

In general, yes.

Allocators should generally be a cheap-to-copy handle to an upstream memory resource.

[shlevy]

Seems like there's consensus, thanks!