Yes, that’s already possible today, they can do anything.
We haven’t decided for sure if we’re going to do this upstream yet, so those kinds of policy questions have yet to be answered. I’d imagine so, but there’s a lot of details there!
I would say precompiled proc macros via wasm narrows that hole - since it can't access any outside source, it becomes deterministic and greatly simplifies testing it for malicous output.
Yes, this particular implementation does. That doesn’t mean the final one will follow suit. This could be considered breaking backwards compatibility, for example.
True. I'd hope future implementations are very explicit about what operations are allowable (for example, globs for files in allowed inputs/outputs), such that you still have an easier time testing.
We haven’t decided for sure if we’re going to do this upstream yet, so those kinds of policy questions have yet to be answered. I’d imagine so, but there’s a lot of details there!