Error code E0552

A unrecognized representation attribute was used.

Erroneous code example:

#![allow(unused)]
fn main() {
#[repr(D)] // error: unrecognized representation hint
struct MyStruct {
    my_field: usize
}
}

You can use a repr attribute to tell the compiler how you want a struct or enum to be laid out in memory.

Make sure you’re using one of the supported options:

#![allow(unused)]
fn main() {
#[repr(C)] // ok!
struct MyStruct {
    my_field: usize
}
}

For more information about specifying representations, see the “Alternative Representations” section of the Rustonomicon.