internal `fn propagate_recursive` is unsound (unexploitably)

[BoxyUwU]

this code is incorrect as the function is not marked unsafe. a caller could already have a borrow from that query out on Entity which would lead to aliasing & and &mut

cc @james7132 since this was discussed on discord in the ecs-dev channel

[joseph-gio]

a caller could already have a borrow from that query out on Entity which would lead to aliasing & and &mut

I don't think this is true, the borrow checker should handle this one. The parameter unsafe_transform_query is of type &Query<&mut T>, so the caller would need to use unsafe code in order to get an aliased reference.

Apologies if I'm missing something, I couldn't find the original discord discussion.

Edit: I forgot that you can still call Query::get on a query that does not implement ReadOnlyWorldQuery.