error[E0782]: trait objects must include the dyn keyword

[Chaoses-Ib]

Source code:

use interoptopus::Error;
use interoptopus::patterns::result::{FFIError};
use interoptopus::{ffi_type, ffi_service, ffi_service_ctor};
use std::ffi::CString;

/// Some struct we want to expose as a class.
#[ffi_type(opaque)]
#[derive(Default)]
pub struct SimpleService {
    pub some_value: u32,
    pub c_string: CString,
    pub data: Vec<u32>,
}

// Regular implementation of methods.
#[ffi_service(error = "FFIError", prefix = "simple_service_")]
impl SimpleService {
    /// The constructor must return a `Result<Self, Error>`.
    #[ffi_service_ctor]
    pub fn new_with(some_value: u32) -> Result<Self, Error> {
        Ok(Self {
            some_value,
            c_string: CString::new("Hello new_with").unwrap(),
            data: vec![some_value; some_value as usize],
        })
    }
}

Build log:

> cargo +nightly build
error[E0782]: trait objects must include the `dyn` keyword
  --> ...\src\lib.rs:18:5
   |
18 | /     /// The constructor must return a `Result<Self, Error>`.
19 | |     #[ffi_service_ctor]
20 | |     pub fn new_with(some_value: u32) -> Result<Self, Error> {
21 | |         Ok(Self {
...  |
25 | |         })
26 | |     }
   | |_____^
   |
help: add `dyn` keyword before this trait
   |
18 |     dyn /// The constructor must return a `Result<Self, Error>`.
   |     +++

error[E0782]: trait objects must include the `dyn` keyword
  --> ...\src\lib.rs:17:1
   |
17 | / impl SimpleService {
18 | |     /// The constructor must return a `Result<Self, Error>`.
19 | |     #[ffi_service_ctor]
20 | |     pub fn new_with(some_value: u32) -> Result<Self, Error> {
...  |
26 | |     }
27 | | }
   | |_^
   |
help: add `dyn` keyword before this trait
   |
17 | dyn impl SimpleService {
   | +++

For more information about this error, try `rustc --explain E0782`.
error: could not compile `interop` due to 4 previous errors

And if I add dyn before #[ffi_service_ctor], I will get another error:

error: expected item after doc comment
  --> ...\src\lib.rs:18:5
   |
17 | impl SimpleService {
   |                    - while parsing this item list starting here
18 |     /// The constructor must return a `Result<Self, Error>`.
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this doc comment doesn't document anything
...
27 | }
   | - the item list ends here

error: custom attribute panicked
  --> ...\src\lib.rs:16:1
   |
16 | #[ffi_service(error = "FFIError", prefix = "simple_service_")]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: message: Must be item.: Error("expected `!`")

Did I miss something?

[ralfbiedert]

The error message could be better, but if you compare here, you'll also need your own Error and FFIError types:

use interoptopus::{ffi_type, ffi_service, ffi_service_ctor};
use std::ffi::CString;
use std::fmt::{Display, Formatter};

#[ffi_type(patterns(ffi_error))]
#[repr(C)]
pub enum FFIError {
    Ok = 0,
    Null = 100,
    Panic = 200,
    Fail = 300,
}

// This is the error type you use in a Rust library. Again, you are almost
// entirely free how you want to implement it.
#[derive(Debug)]
pub enum Error {
    Bad,
}

// Provide a mapping how your Rust error enums translate
// to your FFI error enums.
impl From<Error> for FFIError {
    fn from(x: Error) -> Self {
        match x {
            Error::Bad => Self::Fail,
        }
    }
}

// Implement Default so we know what the "good" case is.
impl Default for FFIError {
    fn default() -> Self {
        Self::Ok
    }
}

// Implement Interoptopus' `FFIError` trait for your FFIError enum.
// Here you must map 3 "well known" variants to your enum.
impl interoptopus::patterns::result::FFIError for FFIError {
    const SUCCESS: Self = Self::Ok;
    const NULL: Self = Self::Null;
    const PANIC: Self = Self::Panic;
}

// Lazy "Display" implementation so your error can be logged.
impl Display for Error {
    fn fmt(&self, _: &mut Formatter<'_>) -> std::fmt::Result {
        Ok(())
    }
}

// Tell Rust your error type is an actual Rust Error.
impl std::error::Error for Error {}

/// Some struct we want to expose as a class.
#[ffi_type(opaque)]
#[derive(Default)]
pub struct SimpleService {
    pub some_value: u32,
    pub c_string: CString,
    pub data: Vec<u32>,
}

// Regular implementation of methods.
#[ffi_service(error = "FFIError", prefix = "simple_service_")]
impl SimpleService {
    /// The constructor must return a `Result<Self, Error>`.
    #[ffi_service_ctor]
    pub fn new_with(some_value: u32) -> Result<Self, Error> {
        Ok(Self {
            some_value,
            c_string: CString::new("Hello new_with").unwrap(),
            data: vec![some_value; some_value as usize],
        })
    }
}

[Chaoses-Ib]

Thank you, it works. I misunderstood the sample code.