First of all, great write-up! Had a blast reading it :) I think there's a difference between a language giving you a footgun and a library giving you a footgun. Libraries, by definition, are supposed to be as user-friendly as possible.

For example, I can just do `loop { }` which the language is perfectly okay with letting me do anywhere in my code (and essentially hanging execution). But if I'm using a library and I'm calling `innocuous()` and there's a `loop { }` buried somewhere in there, that is (in my opinion) the library's responsibility.

N.B. I don't know enough about tokio's internals to suggest any changes and don't want to pretend like I'm an expert, but I do think this caveat should be clearly documented and a "safe" version of `select!` (which wouldn't work with references) should be provided.