Use the .. syntax in Rust struct literals to copy fields from an existing instance while overriding specific values.
Use the .. syntax inside a struct literal to copy all fields from an existing instance except those you explicitly override.
struct Point { x: i32, y: i32 }
let original = Point { x: 10, y: 20 };
let updated = Point { x: 30, ..original };
// updated is Point { x: 30, y: 20 }
This creates a new Point with x set to 30 while inheriting y from original.
The struct update syntax lets you create a new version of a data object by copying most of its values and changing only the ones you specify. It works like making a photocopy of a form, filling in only the fields that have changed, and leaving the rest as they were. You use this when you need to modify a single property of a complex object without rewriting the entire definition.