The compiler will not compile code it cannot verify as safe (outside an `unsafe` block), meaning it will complain about lifetime constraints that are missing, e

The compiler will not compile code it cannot verify as safe (outside an `unsafe` block), meaning it will complain about lifetime constraints that are missing, e.g. it is a compile-time error to not propagate the lifetime information out of the enum. http://play.rust-lang.org/?run=1&code=enum%20Token%20{%0A%20%20%20%20Word%28%26str%29%2C%0A%20%20%20%20Other%28%26str%29%0A}%0A%0Afn%20main%28%29%20{} http://play.rust-lang.org/?run=1&code=enum%20Token%20{%0A%20...