How to Use std

Use From and Into for infallible conversions, and TryFrom and TryInto for conversions that might fail. Implement From for the source type to define the conversion logic, then use Into automatically via the blanket implementation.

use std::convert::{From, Into, TryFrom, TryInto};

struct MyStruct { value: i32 }

impl From<i32> for MyStruct {
    fn from(val: i32) -> Self {
        MyStruct { value: val }
    }
}

impl TryFrom<u8> for MyStruct {
    type Error = &'static str;
    fn try_from(val: u8) -> Result<Self, Self::Error> {
        if val > 100 {
            Err("Value too large")
        } else {
            Ok(MyStruct { value: val as i32 })
        }
    }
}

fn main() {
    let s: MyStruct = 5.into();
    let s2: Result<MyStruct, _> = 50u8.try_into();
}

These traits are standard ways to change one data type into another. Use From and Into when the conversion is guaranteed to work, like turning a number into a string. Use TryFrom and TryInto when the conversion might fail, like parsing a string that isn't a number, so your program can handle the error safely.