Trait function signatures

January 7, 2022

daybook, rust | permalink

I thought when you implemented a trait, the function had to have the exact same signature as the trait, but apparently you can (at least) change the parameters from being immutable to mutable. This is from rustlings/traits/traits2, the instructions of which said to implement AppendBar on a vector of strings, such that you appended "Bar" to it:

trait AppendBar {
    fn append_bar(self) -> Self;
}

impl AppendBar for Vec<String> {
    fn append_bar(mut self) -> Self {
        self.push("Bar".to_string());
        self
    }
}