A speculative proposal for adding 'profiles' to Rust, declared in Cargo.toml, that would adjust lint settings and error levels without changing runtime semantics. Profiles would let developers declare what kinds of things they want to pay attention to — for example, a high-level application profile could allow implicit clone operations on Rc/Arc, while a low-level/kernel profile would deny them and require explicit clones. The same mechanism could handle implicit boxing in async trait dispatch and panic-effect tracking. The key principle is that profiles never change what code does at runtime, only what warnings or errors are surfaced, so code can be freely moved between projects. The author frames this as a way to make Rust feel more ergonomic for application code while preserving its systems-level rigor for code that needs it.
