On “Viral Annotations”
“Viral annotations” can be seen to as magical solutions to a lot of problems, but it is often frowned upon by PL designers. A major problem is that they need to be annotated bottom-up for every functions in a calling tree.
Examples:
- C++
constexpr,noexcept - CUDA
__device__ - Rust lifetime,
const,async - Others (often in compiler extensions): “pure function”, “don’t lock”, “don’t panic”
Sometimes compilers can infer those annotations, but often not across compilation boundaries.
Solutions to Issues
Compiler Inferences
Rust Lifetimes can often be inferred. It is far from a perfect solution, but is much better than explicitly writing everything.
Escape Hatch
E.g. Rust’s unsafe is somewhat viral but you can use an unsafe block in a “safe” function.