What it does

Warns when struct initialization uses ..Default::default() pattern, to prevent silent initialization of newly added fields (with unwanted values)

Using ..Default::default() can hide field initialization when new fields are added to structs, potentially leading to bugs where developers forget to explicitly set values for new fields.

Advantages

• Prevents accidental use of default values when new fields are added
• Forces developers to make conscious decisions about field values
• Makes code changes more visible during review

Drawbacks

• More boilerplate code required
• Longer struct initializations
• Slows down initial development
• Could be difficult to implement in large existing codebases

Example

struct Config {
    host: String,
    port: u16,
}

let config = Config {
    host: "localhost".to_string(),
    ..Default::default()
};

Could be written as:

let config = Config {
    host: "localhost".to_string(),
    port: 8080,
};