can't swap absl::FixedArray

[leissa]

Describe the issue

You can't swap an absl::FixedArray<T>. There is neither a member function nor does the default std::swap work:
https://godbolt.org/z/3foo8xaPK

Steps to reproduce the problem

see above

What version of Abseil are you using?

trunk

What operating system and version are you using?

godbolt

What compiler and version are you using?

clang 17.0.1

What build system are you using?

godbolt

Additional context

see also #1571

[derekmauro]

I'm not sure the typical use cases for FixedArray are cases for which having a swap method makes sense. FixedArray is usually used for putting a small array on the stack, but with an extent determined at runtime. How does swapping two FixedArrays of differing sizes that are backed with stack memory work? I suspect if you are trying to swap, absl::InlinedVector is a better choice. Can you describe the use case?

[leissa]

My use case is that I need a lot of usually very small arrays which don't need to be resizable and I thought that absl::FixedArray would be a nice fit for that. absl::InlinedVector has the extra capacity that I don't need. But since you can't swap an absl::FixedArray you can't really use that thing for pretty much anything besides local variables.