- Clang (depending on warnings level) may reject a valid program -- doesn't make it less useful, you just suppress the check for the offending line and carry on
- Rust borrow checker may be seemingly picky and reject a perfectly valid program form your viewpoint. Does it make it less useful? I wouldn't say so.
My point is that the validator can't give you the safety property that is claimed as a defence against one of the inherent issues with this approach.
I mostly have a non-malicious user in mind though (i.e. end-user software, where the software and the config have same permissions)
If you do have such security concerns, you probably need a sandbox at some point. E.g. big source of my frustration are CI pipelines -- they run isolated anyway and execute arbitrary code. Having a YAML there does nothing for the security.