[Rust] Generic

Example 1:

fn main() {
    let mut shopping_list: Vec<&str> = Vec::new();
    shopping_list.push("milk");
}

Example 2:

struct Wrapper<T> {
    value: T,
}

impl<T> Wrapper<T> {
    pub fn new(value: T) -> Self {
        Wrapper { value }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn store_u32_in_wrapper() {
        assert_eq!(Wrapper::new(42).value, 42);
    }

    #[test]
    fn store_str_in_wrapper() {
        assert_eq!(Wrapper::new("Foo").value, "Foo");
    }
}

Example 3: Constraining generics using traits impl<T: std::fmt::Display>

pub struct ReportCard<T> {
    pub grade: T,
    pub student_name: String,
    pub student_age: u8,
}

impl<T: std::fmt::Display> ReportCard<T> {
    pub fn print(&self) -> String {
        format!("{} ({}) - achieved a grade of {}",
            &self.student_name, &self.student_age, &self.grade)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn generate_numeric_report_card() {
        let report_card = ReportCard {
            grade: "2.1",
            student_name: "Tom Wriggle".to_string(),
            student_age: 12,
        };
        assert_eq!(
            report_card.print(),
            "Tom Wriggle (12) - achieved a grade of 2.1"
        );
    }

    #[test]
    fn generate_alphabetic_report_card() {
        // TODO: Make sure to change the grade here after you finish the exercise.
        let report_card = ReportCard {
            grade: "A+",
            student_name: "Gary Plotter".to_string(),
            student_age: 11,
        };
        assert_eq!(
            report_card.print(),
            "Gary Plotter (11) - achieved a grade of A+"
        );
    }
}