E0407: Linear struct copy

Explanation

A struct was declared both linear and @copy. Linear values must have one tracked consumption, while Copy values may be duplicated implicitly.

Likely cause

The @copy directive was applied to a linear struct, combining incompatible ownership promises. Remove @copy and consume each linear value, or remove linear if freely duplicating the value is the intended behavior.

Examples

Linear struct marked @copy

@copy
linear struct Token { value: i32 }
fn main() -> i32 { 0 }

Keep the value linear and consume it

linear struct Token { value: i32 }
fn consume(token: Token) -> i32 { token.value }
fn main() -> i32 {
    let token = Token { value: 42 };
    consume(token)
}

References

• Linear structs cannot be Copy