Zero-cost to whom? The developer? no as now the implementation details have to be known, the machine? no as time will be spent in the compiler churning away rem

Zero-cost to whom? The developer? no as now the implementation details have to be known, the machine? no as time will be spent in the compiler churning away removing junk or if the compiler isn't smart enough including it. Also the C++ / rust definition of zero-cost is only if you don't use the abstraction. Minimal runtime is relative.