I believe they use a GC, so they may be able to leverage the runtime to help out. If it's all type system-based, the compiler probably has to be stricter to ens

I believe they use a GC, so they may be able to leverage the runtime to help out. If it's all type system-based, the compiler probably has to be stricter to ensure safety (Rice's theorem implies that compilers err on the side of rejecting some valid programs in order to reject all invalid programs). Maybe Pony could be a blend of Erlang and Rust?