structs.md

Structs

Use Default::default for initializing struct fields without a specific value.

Use ..struct notation to shorten struct initialization, especially when initializing most fields of a struct to its default implementation.

Example

Don't do:

struct Test {
    field1: usize,
    field2: usize,
    field3: usize,
}

impl Default for Test {
    fn default() -> Self {
        Self {
            field1: 0,
            field2: 13,
            field3: 0,
        }
    }
}

impl Test {
    fn new(field1: usize) -> Self {
        Self {
            field1,
            field2: 13,
            field3: 0,
        }
    }
}

Do instead:

struct Test {
    field1: usize,
    field2: usize,
    field3: usize,
}

impl Default for Test {
    fn default() -> Self {
        Self {
            field2: 13,
            field1: Default::default(),
            field3: Default::default(),
        }
    }
}

impl Test {
    fn new(field1: usize) -> Self {
        Self {
            field1,
            ..Default::default()
        }
    }
}

Explanation

Initializing struct fields with Default::default can make it more clear to a reader that the chosen value is of no special significance. Additionally for Default implementations it makes it obvious which values prevent the derivation of the Default trait.

Using the ..struct shorthand not only makes it clear that only part of a struct is explicitly overridden, it also automatically applies future changes to the parts that are copied from the other struct.