Comment by cesarb

> The obvious implementation is for unsafe to be infectious like const. You have unsafe code, your crate is unsafe. You depend on an unsafe crate, your crate becomes unsafe.

That would mean everything is unsafe, since every crate depends on core (or on std which depends on core), which has "unsafe" code.

The design of "unsafe" in Rust, instead, is to allow building safe abstractions on top of unsafe code (or be able to clearly mark when the abstraction itself is unsafe). That way, for instance, users of `Vec::push` do not have to worry that it uses uninitialized memory (which is unsafe).