Cargo Features

Iron has no features set by default.

iron = { version = "0.6.1", features = ["native-tls-example"] }
native-tls-example = hyper-native-tls

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

hyper-native-tls native-tls-example?