E0403: Copy struct non copy field

Explanation

A struct marked @copy contains a field whose type has move semantics. Implicitly duplicating the outer value would also have to duplicate that non-Copy field.

Likely cause

A field is a struct without @copy, a move-typed aggregate, or another type that cannot be implicitly duplicated. Remove @copy from the outer struct or make every field type Copy when that is semantically valid.

Examples

Non-Copy field in a @copy struct

struct Inner { value: i32 }
@copy
struct Outer { inner: Inner }
fn main() -> i32 { 0 }

Use only Copy field types

@copy
struct Inner { value: i32 }
@copy
struct Outer { inner: Inner }
fn main() -> i32 {
    let outer = Outer { inner: Inner { value: 42 } };
    let duplicate = outer;
    outer.inner.value + duplicate.inner.value
}

References

• Copy struct field requirement