Rust error E0552: #### Note: this error code is no longer emitted by the compiler. This error code was replaced by `E0539`

The compiler team's explanation

Note: this error code is no longer emitted by the compiler.

This error code was replaced by E0539.

A unrecognized representation attribute was used.

Erroneous code example:

#[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:

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

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

From rustc --explain E0552 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.