[erlang-questions] Illegal Guard?

[Unix One]

On 02/08/2016 05:18 PM, Richard A. O'Keefe wrote:

> Note also, as the paper linked above certainly does,
> that hot-loading means that you can never be certain
> that a function from another module will be pure when
> you call it.

Please excuse my ignorance, but wouldn't this specific point potentially 
not be an issue if:

- guards required functions to be explicitly declared pure
- compiler verified the assertion of purity
- hot code loader refused to load if a guard function wasn't declared pure

Maybe the declaration of purity is not necessarily required, but it does 
make it more explicit.

Thank you.