Created
May 31, 2020 12:43
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| mod states { | |
| pub struct Red; | |
| pub struct Yellow; | |
| pub struct Green; | |
| } | |
| fn red(_traffic_light: &TrafficLight<states::Red>) {} | |
| fn yellow(_traffic_light: &TrafficLight<states::Yellow>) {} | |
| fn green(_traffic_light: &TrafficLight<states::Green>) {} | |
| struct TrafficLight<COLOR> { | |
| _color: COLOR, | |
| } | |
| impl TrafficLight<states::Red> { | |
| fn new() -> TrafficLight<states::Red> { | |
| TrafficLight { | |
| _color: states::Red, | |
| } | |
| } | |
| } | |
| impl TrafficLight<states::Red> { | |
| fn next(&self) -> TrafficLight<states::Yellow> { | |
| TrafficLight { | |
| _color: states::Yellow, | |
| } | |
| } | |
| } | |
| impl TrafficLight<states::Yellow> { | |
| fn next(&self) -> TrafficLight<states::Green> { | |
| TrafficLight { | |
| _color: states::Green, | |
| } | |
| } | |
| } | |
| impl TrafficLight<states::Green> { | |
| fn next(&self) -> TrafficLight<states::Red> { | |
| TrafficLight { | |
| _color: states::Red, | |
| } | |
| } | |
| } | |
| fn main() { | |
| let traffic_light = TrafficLight::new(); | |
| red(&traffic_light); | |
| // compile error | |
| // yellow(&traffic_light); | |
| let traffic_light = traffic_light.next(); | |
| yellow(&traffic_light); | |
| // compile error | |
| // green(&traffic_light); | |
| let traffic_light = traffic_light.next(); | |
| green(&traffic_light); | |
| // compile error | |
| // red(&traffic_light); | |
| let traffic_light = traffic_light.next(); | |
| red(&traffic_light); | |
| // compile error | |
| // yellow(&traffic_light); | |
| } |
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