Static DEFAULT_OVERRIDES_DEFAULT_FIELDS

pub static DEFAULT_OVERRIDES_DEFAULT_FIELDS: &Lint

The default_overrides_default_fields lint checks for manual impl blocks of the Default trait of types with default field values.

Example

#![feature(default_field_values)]
struct Foo {
    x: i32 = 101,
    y: NonDefault,
}

struct NonDefault;

#[deny(default_overrides_default_fields)]
impl Default for Foo {
    fn default() -> Foo {
        Foo { x: 100, y: NonDefault }
    }
}

{{produces}}

Explanation

Manually writing a Default implementation for a type that has default field values runs the risk of diverging behavior between Type { .. } and <Type as Default>::default(), which would be a foot-gun for users of that type that would expect these to be equivalent. If Default can’t be derived due to some fields not having a Default implementation, we encourage the use of .. for the fields that do have a default field value.