Lint for iterating over the keys in an unordered collection such as HashSet or HashMap

[kayabaNerve]

What it does

A (possibly pedantic) lint for iterating over a HashSet/HashMap would be appreciated. Given these do not stable iteration orders across program instances, any usage of them in redundant systems may cause differing results and inconsistencies. They also have an unclear iteration order (not lexicographical to keys nor by order) which may give adverse effects in a variety of other use cases.

In effect, the same as rust-lang/rust#92584 (which I would appreciate if anyone could give me insight on how to fork/run over my own project now, possibly via dylint).

Advantage

No response

Drawbacks

No response

Example

for (key, value) in my_map {}

Could be written as:

let mut keys = my_map.keys().clone().collect::<Vec<_>();
keys.sort();
for key in keys {
  let value = &my_map[value];
}

Please note I don't actually endorse the suggested alternative. My usages of map iteration frequently have context which show how iteration should occur. Without said context, my example is forced to create a slow but safe migration for this lint topic.

[Jarcho]

This is definitely a restriction lint, but it does have it's uses.

[Jacherr]

@rustbot claim

[kayabaNerve]

Thank you @Jacherr!