[rust] import/export type mismatch in generated Rust stuff

[jcbhmr]

this problem of "phantom imports" from here WebAssembly/component-model#295 (comment) https://github.com/jcbhmr/unicode-math-class.wasm/actions/runs/7631660252

Details

package typst-community:unicode-math-class@2.0.0+0.1.0;

interface types {
    /// <https://docs.rs/unicode-math-class/0.1.0/unicode_math_class/enum.MathClass.html>
    enum math-class {
        normal,
        alphabetic,
        binary,
        closing,
        diacritic,
        fence,
        glyph-part,
        large,
        opening,
        punctuation,
        relation,
        space,
        unary,
        vary,
        special,
    }
}

/// <https://docs.rs/unicode-math-class/0.1.0/unicode_math_class/>
world unicode-math-class {
    export types;
    use types.{math-class};

    /// <https://docs.rs/unicode-math-class/0.1.0/unicode_math_class/constant.REVISION.html>
    export revision: func() -> u8;

    /// <https://docs.rs/unicode-math-class/0.1.0/unicode_math_class/fn.class.html>
    export class: func(c: string) -> option<math-class>;
}

mod my_macros;

cargo_component_bindings::generate!();
use my_macros::rs_wit_parallel_enum;
use unicode_math_class;

pub struct Component;
impl bindings::Guest for Component {
    fn revision() -> u8 {
        unicode_math_class::REVISION
    }
    fn class(c: String) -> Option<bindings::MathClass> {
        let c = c.chars().next().expect("non-empty string");
        unicode_math_class::class(c).map(|x| x.into())
    }
}

rs_wit_parallel_enum!(unicode_math_class::MathClass, bindings::MathClass, {
    Normal,
    Alphabetic,
    Binary,
    Closing,
    Diacritic,
    Fence,
    GlyphPart,
    Large,
    Opening,
    Punctuation,
    Relation,
    Space,
    Unary,
    Vary,
    Special,
});

// wasm-tools component wit

package root:component;

world root {
  import typst-community:unicode-math-class/types@2.0.0+0.1.0;
  use typst-community:unicode-math-class/types@2.0.0+0.1.0.{math-class};

  export revision: func() -> u8;
  export class: func(c: string) -> option<math-class>;
  export typst-community:unicode-math-class/types@2.0.0+0.1.0;
}

https://github.com/jcbhmr/unicode-math-class.wasm/tree/fe20eb02987a2a41855fcbe4bee78475f4becb07

has happened to me again in a much worse way; cargo-component (which uses wit-bindgen iirc) is using this phantom imported type instead of the locally declared exported type which has the needed data (the 0th tuple item) that i need to use to perform various library operations.

here's the wit:
im trying to provide bindings for this https://docs.rs/subsetter/latest/subsetter/ rust crate in wit

package typst-community:subsetter@1.0.0+0.1.1;

interface types {
  resource profile {
    pdf: static func(glyphs: list<u16>) -> profile;
  }

  record tag {
    tuple0: tuple<u8, u8, u8, u8>,
  }

  variant error {
    unknown-kind,
    invalid-offset,
    missing-data,
    invalid-data,
    missing-table(tag),
  }
}

world subsetter {
  export types;
  use types.{profile, tag, error};

  export subset: func(data: list<u8>, index: u32, profile: profile) -> result<list<u8>, error>;
}

and here's the code

cargo_component_bindings::generate!();
use bindings::exports::typst_community::subsetter::types;
use subsetter;

pub struct Component;
impl bindings::Guest for Component {
    // SHOULD BE using the bindings::exports::* stuff
    // fn subset(data: Vec<u8>, index: u32, profile: types::Profile) -> Result<Vec<u8>, types::Error> {
    //     todo!()
    // }

    // BUT IS using the IMPORTED types which means I can't extract the
    // inner tuple 0 item from the profile struct to operate on it
    fn subset(
        data: Vec<u8>,
        index: u32,
        profile: bindings::typst_community::subsetter::types::Profile,
    ) -> Result<Vec<u8>, bindings::typst_community::subsetter::types::Error> {
        todo!()
    }
}

pub struct Profile(subsetter::Profile<'static>);
impl types::GuestProfile for Profile {
    fn pdf(glyphs: Vec<u16>) -> types::OwnProfile {
        todo!()
    }
}

and when that compiles (with using the rust code as shown above) it gives some weird wit when using wasm-tools component wit

@jcbhmr ➜ /workspaces/subsetter.wasm (main) $ wasm-tools component wit ./target/wasm32-unknown-unknown/debug/subsetter.wasm 
package root:component;

world root {
  import typst-community:subsetter/types@1.0.0+0.1.1;
  use typst-community:subsetter/types@1.0.0+0.1.1.{profile, tag, error};

  export subset: func(data: list<u8>, index: u32, profile: profile) -> result<list<u8>, error>;
  export typst-community:subsetter/types@1.0.0+0.1.1;
}

reproduction: https://github.com/jcbhmr/subsetter.wasm/tree/9b1d7c65a48bdb9a92f6d3bf48ee97b8485fbb64

basically what i understand to be happening in error is that the use types.{...} is somehow importing the things from the interface types {}? and then when it generates the rust bindings.rs it generates the imported types and then uses those imported types instead of the exported types that i want it to use.

the end result is that i cannot get the profile.0. 🤷‍♂️
idk if im even explaining this right or what. all i know is that the types that i want and the types that i got are mismatched and idk what to do if this is a bug or if this is how WIT is supposed to work or what lol

cc @lukewagner

Details

bindings.rs copy pasted here

// Generated by `wit-bindgen` 0.16.0. DO NOT EDIT!
pub type Profile = typst_community::subsetter::types::Profile;
pub type Error = typst_community::subsetter::types::Error;
const _: () = {
  
  #[doc(hidden)]
  #[export_name = "subset"]
  #[allow(non_snake_case)]
  unsafe extern "C" fn __export_subset(arg0: i32,arg1: i32,arg2: i32,arg3: i32,) -> i32 {
    #[allow(unused_imports)]
    use ::cargo_component_bindings::rt::{alloc, vec::Vec, string::String};
    
    // Before executing any other code, use this function to run all static
    // constructors, if they have not yet been run. This is a hack required
    // to work around wasi-libc ctors calling import functions to initialize
    // the environment.
    //
    // This functionality will be removed once rust 1.69.0 is stable, at which
    // point wasi-libc will no longer have this behavior.
    //
    // See
    // https://github.com/bytecodealliance/preview2-prototyping/issues/99
    // for more details.
    #[cfg(target_arch="wasm32")]
    ::cargo_component_bindings::rt::run_ctors_once();
    
    let len0 = arg1 as usize;
    let result1 = <_GuestImpl as Guest>::subset(Vec::from_raw_parts(arg0 as *mut _, len0, len0), arg2 as u32, typst_community::subsetter::types::Profile::from_handle(arg3 as u32));
    let ptr2 = _RET_AREA.0.as_mut_ptr() as i32;
    match result1 {
      Ok(e) => { {
        *((ptr2 + 0) as *mut u8) = (0i32) as u8;
        let vec3 = (e).into_boxed_slice();
        let ptr3 = vec3.as_ptr() as i32;
        let len3 = vec3.len() as i32;
        ::core::mem::forget(vec3);
        *((ptr2 + 8) as *mut i32) = len3;
        *((ptr2 + 4) as *mut i32) = ptr3;
      } },
      Err(e) => { {
        *((ptr2 + 0) as *mut u8) = (1i32) as u8;
        use typst_community::subsetter::types::Error as V6;
        match e {
          V6::UnknownKind=> {
            {
              *((ptr2 + 4) as *mut u8) = (0i32) as u8;
            }
          }
          V6::InvalidOffset=> {
            {
              *((ptr2 + 4) as *mut u8) = (1i32) as u8;
            }
          }
          V6::MissingData=> {
            {
              *((ptr2 + 4) as *mut u8) = (2i32) as u8;
            }
          }
          V6::InvalidData=> {
            {
              *((ptr2 + 4) as *mut u8) = (3i32) as u8;
            }
          }
          V6::MissingTable(e) => {
            *((ptr2 + 4) as *mut u8) = (4i32) as u8;
            let typst_community::subsetter::types::Tag{ tuple0:tuple04, } = e;
            let (t5_0, t5_1, t5_2, t5_3, ) = tuple04;
            *((ptr2 + 5) as *mut u8) = (::cargo_component_bindings::rt::as_i32(t5_0)) as u8;
            *((ptr2 + 6) as *mut u8) = (::cargo_component_bindings::rt::as_i32(t5_1)) as u8;
            *((ptr2 + 7) as *mut u8) = (::cargo_component_bindings::rt::as_i32(t5_2)) as u8;
            *((ptr2 + 8) as *mut u8) = (::cargo_component_bindings::rt::as_i32(t5_3)) as u8;
          },
        }
      } },
    };ptr2
  }
  
  const _: () = {
    #[doc(hidden)]
    #[export_name = "cabi_post_subset"]
    #[allow(non_snake_case)]
    unsafe extern "C" fn __post_return_subset(arg0: i32,) {
      let l0 = i32::from(*((arg0 + 0) as *const u8));
      match l0 {
        0 => {
          let l1 = *((arg0 + 4) as *const i32);
          let l2 = *((arg0 + 8) as *const i32);
          let base3 = l1;
          let len3 = l2;
          ::cargo_component_bindings::rt::dealloc(base3, (len3 as usize) * 1, 1);
        },
        _ => (),
      }
    }
  };
};
use super::Component as _GuestImpl;
pub trait Guest {
  fn subset(data: ::cargo_component_bindings::rt::vec::Vec::<u8>,index: u32,profile: Profile,) -> Result<::cargo_component_bindings::rt::vec::Vec::<u8>,Error>;
}

#[allow(unused_imports)]
use ::cargo_component_bindings::rt::{alloc, vec::Vec, string::String};

#[repr(align(4))]
struct _RetArea([u8; 12]);
static mut _RET_AREA: _RetArea = _RetArea([0; 12]);
pub mod typst_community {
  pub mod subsetter {
    
    #[allow(clippy::all)]
    pub mod types {
      #[used]
      #[doc(hidden)]
      #[cfg(target_arch = "wasm32")]
      static __FORCE_SECTION_REF: fn() = super::super::super::__link_section;
      
      #[derive(Debug)]
      #[repr(transparent)]
      pub struct Profile{
        handle: ::cargo_component_bindings::rt::Resource<Profile>,
      }
      
      impl Profile{
        #[doc(hidden)]
        pub unsafe fn from_handle(handle: u32) -> Self {
          Self {
            handle: ::cargo_component_bindings::rt::Resource::from_handle(handle),
          }
        }
        
        #[doc(hidden)]
        pub fn into_handle(self) -> u32 {
          ::cargo_component_bindings::rt::Resource::into_handle(self.handle)
        }
        
        #[doc(hidden)]
        pub fn handle(&self) -> u32 {
          ::cargo_component_bindings::rt::Resource::handle(&self.handle)
        }
      }
      
      
      unsafe impl ::cargo_component_bindings::rt::WasmResource for Profile{
        #[inline]
        unsafe fn drop(_handle: u32) {
          #[cfg(not(target_arch = "wasm32"))]
          unreachable!();
          
          #[cfg(target_arch = "wasm32")]
          {
            #[link(wasm_import_module = "typst-community:subsetter/types@1.0.0+0.1.1")]
            extern "C" {
              #[link_name = "[resource-drop]profile"]
              fn drop(_: u32);
            }
            
            drop(_handle);
          }
        }
      }
      
      #[repr(C)]
      #[derive(Clone, Copy)]
      pub struct Tag {
        pub tuple0: (u8,u8,u8,u8,),
      }
      impl ::core::fmt::Debug for Tag {
        fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
          f.debug_struct("Tag").field("tuple0", &self.tuple0).finish()
        }
      }
      #[derive(Clone, Copy)]
      pub enum Error{
        UnknownKind,
        InvalidOffset,
        MissingData,
        InvalidData,
        MissingTable(Tag),
      }
      impl ::core::fmt::Debug for Error {
        fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
          match self {
            Error::UnknownKind => {
              f.debug_tuple("Error::UnknownKind").finish()
            }
            Error::InvalidOffset => {
              f.debug_tuple("Error::InvalidOffset").finish()
            }
            Error::MissingData => {
              f.debug_tuple("Error::MissingData").finish()
            }
            Error::InvalidData => {
              f.debug_tuple("Error::InvalidData").finish()
            }
            Error::MissingTable(e) => {
              f.debug_tuple("Error::MissingTable").field(e).finish()
            }
          }
        }
      }
      impl ::core::fmt::Display for Error {
        fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
          write!(f, "{:?}", self)
        }
      }
      
      impl std::error::Error for Error {}
      impl Profile {
        #[allow(unused_unsafe, clippy::all)]
        pub fn pdf(glyphs: &[u16],) -> Profile{
          
          #[allow(unused_imports)]
          use ::cargo_component_bindings::rt::{alloc, vec::Vec, string::String};
          unsafe {
            let vec0 = glyphs;
            let ptr0 = vec0.as_ptr() as i32;
            let len0 = vec0.len() as i32;
            
            #[cfg(target_arch = "wasm32")]
            #[link(wasm_import_module = "typst-community:subsetter/types@1.0.0+0.1.1")]
            extern "C" {
              #[link_name = "[static]profile.pdf"]
              fn wit_import(_: i32, _: i32, ) -> i32;
            }
            
            #[cfg(not(target_arch = "wasm32"))]
            fn wit_import(_: i32, _: i32, ) -> i32{ unreachable!() }
            let ret = wit_import(ptr0, len0);
            Profile::from_handle(ret as u32)
          }
        }
      }
      
    }
    
  }
}
pub mod exports {
  pub mod typst_community {
    pub mod subsetter {
      
      #[allow(clippy::all)]
      pub mod types {
        #[used]
        #[doc(hidden)]
        #[cfg(target_arch = "wasm32")]
        static __FORCE_SECTION_REF: fn() = super::super::super::super::__link_section;
        
        pub use super::super::super::super::super::Profile as Profile;
        const _: () = {
          #[doc(hidden)]
          #[export_name = "typst-community:subsetter/types@1.0.0+0.1.1#[dtor]profile"]
          #[allow(non_snake_case)]
          unsafe extern "C" fn dtor(rep: usize) {
            ::cargo_component_bindings::rt::Resource::<Profile>::dtor(rep)
          }
        };
        unsafe impl ::cargo_component_bindings::rt::RustResource for Profile{
          unsafe fn new(_rep: usize) -> u32 {
            #[cfg(not(target_arch = "wasm32"))]
            unreachable!();
            
            #[cfg(target_arch = "wasm32")]
            {
              #[link(wasm_import_module = "[export]typst-community:subsetter/types@1.0.0+0.1.1")]
              extern "C" {
                #[link_name = "[resource-new]profile"]
                fn new(_: usize) -> u32;
              }
              new(_rep)
            }
          }
          
          unsafe fn rep(_handle: u32) -> usize {
            #[cfg(not(target_arch = "wasm32"))]
            unreachable!();
            
            #[cfg(target_arch = "wasm32")]
            {
              #[link(wasm_import_module = "[export]typst-community:subsetter/types@1.0.0+0.1.1")]
              extern "C" {
                #[link_name = "[resource-rep]profile"]
                fn rep(_: u32) -> usize;
              }
              rep(_handle)
            }
          }
        }
        pub type OwnProfile = ::cargo_component_bindings::rt::Resource<Profile>;
        
        
        unsafe impl ::cargo_component_bindings::rt::WasmResource for Profile{
          #[inline]
          unsafe fn drop(_handle: u32) {
            #[cfg(not(target_arch = "wasm32"))]
            unreachable!();
            
            #[cfg(target_arch = "wasm32")]
            {
              #[link(wasm_import_module = "[export]typst-community:subsetter/types@1.0.0+0.1.1")]
              extern "C" {
                #[link_name = "[resource-drop]profile"]
                fn drop(_: u32);
              }
              
              drop(_handle);
            }
          }
        }
        
        #[repr(C)]
        #[derive(Clone, Copy)]
        pub struct Tag {
          pub tuple0: (u8,u8,u8,u8,),
        }
        impl ::core::fmt::Debug for Tag {
          fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
            f.debug_struct("Tag").field("tuple0", &self.tuple0).finish()
          }
        }
        #[derive(Clone, Copy)]
        pub enum Error{
          UnknownKind,
          InvalidOffset,
          MissingData,
          InvalidData,
          MissingTable(Tag),
        }
        impl ::core::fmt::Debug for Error {
          fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
            match self {
              Error::UnknownKind => {
                f.debug_tuple("Error::UnknownKind").finish()
              }
              Error::InvalidOffset => {
                f.debug_tuple("Error::InvalidOffset").finish()
              }
              Error::MissingData => {
                f.debug_tuple("Error::MissingData").finish()
              }
              Error::InvalidData => {
                f.debug_tuple("Error::InvalidData").finish()
              }
              Error::MissingTable(e) => {
                f.debug_tuple("Error::MissingTable").field(e).finish()
              }
            }
          }
        }
        impl ::core::fmt::Display for Error {
          fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
            write!(f, "{:?}", self)
          }
        }
        
        impl std::error::Error for Error {}
        const _: () = {
          
          #[doc(hidden)]
          #[export_name = "typst-community:subsetter/types@1.0.0+0.1.1#[static]profile.pdf"]
          #[allow(non_snake_case)]
          unsafe extern "C" fn __export_static_profile_pdf(arg0: i32,arg1: i32,) -> i32 {
            #[allow(unused_imports)]
            use ::cargo_component_bindings::rt::{alloc, vec::Vec, string::String};
            
            // Before executing any other code, use this function to run all static
            // constructors, if they have not yet been run. This is a hack required
            // to work around wasi-libc ctors calling import functions to initialize
            // the environment.
            //
            // This functionality will be removed once rust 1.69.0 is stable, at which
            // point wasi-libc will no longer have this behavior.
            //
            // See
            // https://github.com/bytecodealliance/preview2-prototyping/issues/99
            // for more details.
            #[cfg(target_arch="wasm32")]
            ::cargo_component_bindings::rt::run_ctors_once();
            
            let len0 = arg1 as usize;
            let result1 = <_ProfileImpl as GuestProfile>::pdf(Vec::from_raw_parts(arg0 as *mut _, len0, len0));
            ::cargo_component_bindings::rt::Resource::into_handle(result1) as i32
          }
        };
        use super::super::super::super::super::Profile as _ProfileImpl;
        pub trait GuestProfile {
          fn pdf(glyphs: ::cargo_component_bindings::rt::vec::Vec::<u16>,) -> OwnProfile;
        }
        
      }
      
    }
  }
}

#[cfg(target_arch = "wasm32")]
#[link_section = "component-type:subsetter"]
#[doc(hidden)]
pub static __WIT_BINDGEN_COMPONENT_TYPE: [u8; 998] = [3, 0, 9, 115, 117, 98, 115, 101, 116, 116, 101, 114, 0, 97, 115, 109, 13, 0, 1, 0, 7, 229, 1, 1, 65, 2, 1, 66, 10, 4, 0, 7, 112, 114, 111, 102, 105, 108, 101, 3, 1, 1, 111, 4, 125, 125, 125, 125, 1, 114, 1, 6, 116, 117, 112, 108, 101, 48, 1, 4, 0, 3, 116, 97, 103, 3, 0, 2, 1, 113, 5, 12, 117, 110, 107, 110, 111, 119, 110, 45, 107, 105, 110, 100, 0, 0, 14, 105, 110, 118, 97, 108, 105, 100, 45, 111, 102, 102, 115, 101, 116, 0, 0, 12, 109, 105, 115, 115, 105, 110, 103, 45, 100, 97, 116, 97, 0, 0, 12, 105, 110, 118, 97, 108, 105, 100, 45, 100, 97, 116, 97, 0, 0, 13, 109, 105, 115, 115, 105, 110, 103, 45, 116, 97, 98, 108, 101, 1, 3, 0, 4, 0, 5, 101, 114, 114, 111, 114, 3, 0, 4, 1, 112, 123, 1, 105, 0, 1, 64, 1, 6, 103, 108, 121, 112, 104, 115, 6, 0, 7, 4, 0, 19, 91, 115, 116, 97, 116, 105, 99, 93, 112, 114, 111, 102, 105, 108, 101, 46, 112, 100, 102, 1, 8, 4, 1, 43, 116, 121, 112, 115, 116, 45, 99, 111, 109, 109, 117, 110, 105, 116, 121, 58, 115, 117, 98, 115, 101, 116, 116, 101, 114, 47, 116, 121, 112, 101, 115, 64, 49, 46, 48, 46, 48, 43, 48, 46, 49, 46, 49, 5, 0, 11, 11, 1, 0, 5, 116, 121, 112, 101, 115, 3, 0, 0, 7, 239, 4, 1, 65, 2, 1, 65, 15, 1, 66, 10, 4, 0, 7, 112, 114, 111, 102, 105, 108, 101, 3, 1, 1, 111, 4, 125, 125, 125, 125, 1, 114, 1, 6, 116, 117, 112, 108, 101, 48, 1, 4, 0, 3, 116, 97, 103, 3, 0, 2, 1, 113, 5, 12, 117, 110, 107, 110, 111, 119, 110, 45, 107, 105, 110, 100, 0, 0, 14, 105, 110, 118, 97, 108, 105, 100, 45, 111, 102, 102, 115, 101, 116, 0, 0, 12, 109, 105, 115, 115, 105, 110, 103, 45, 100, 97, 116, 97, 0, 0, 12, 105, 110, 118, 97, 108, 105, 100, 45, 100, 97, 116, 97, 0, 0, 13, 109, 105, 115, 115, 105, 110, 103, 45, 116, 97, 98, 108, 101, 1, 3, 0, 4, 0, 5, 101, 114, 114, 111, 114, 3, 0, 4, 1, 112, 123, 1, 105, 0, 1, 64, 1, 6, 103, 108, 121, 112, 104, 115, 6, 0, 7, 4, 0, 19, 91, 115, 116, 97, 116, 105, 99, 93, 112, 114, 111, 102, 105, 108, 101, 46, 112, 100, 102, 1, 8, 3, 1, 43, 116, 121, 112, 115, 116, 45, 99, 111, 109, 109, 117, 110, 105, 116, 121, 58, 115, 117, 98, 115, 101, 116, 116, 101, 114, 47, 116, 121, 112, 101, 115, 64, 49, 46, 48, 46, 48, 43, 48, 46, 49, 46, 49, 5, 0, 2, 3, 0, 0, 7, 112, 114, 111, 102, 105, 108, 101, 3, 0, 7, 112, 114, 111, 102, 105, 108, 101, 3, 0, 1, 2, 3, 0, 0, 3, 116, 97, 103, 3, 0, 3, 116, 97, 103, 3, 0, 3, 2, 3, 0, 0, 5, 101, 114, 114, 111, 114, 3, 0, 5, 101, 114, 114, 111, 114, 3, 0, 5, 1, 112, 125, 1, 105, 2, 1, 106, 1, 7, 1, 6, 1, 64, 3, 4, 100, 97, 116, 97, 7, 5, 105, 110, 100, 101, 120, 121, 7, 112, 114, 111, 102, 105, 108, 101, 8, 0, 9, 4, 0, 6, 115, 117, 98, 115, 101, 116, 1, 10, 1, 66, 10, 4, 0, 7, 112, 114, 111, 102, 105, 108, 101, 3, 1, 1, 111, 4, 125, 125, 125, 125, 1, 114, 1, 6, 116, 117, 112, 108, 101, 48, 1, 4, 0, 3, 116, 97, 103, 3, 0, 2, 1, 113, 5, 12, 117, 110, 107, 110, 111, 119, 110, 45, 107, 105, 110, 100, 0, 0, 14, 105, 110, 118, 97, 108, 105, 100, 45, 111, 102, 102, 115, 101, 116, 0, 0, 12, 109, 105, 115, 115, 105, 110, 103, 45, 100, 97, 116, 97, 0, 0, 12, 105, 110, 118, 97, 108, 105, 100, 45, 100, 97, 116, 97, 0, 0, 13, 109, 105, 115, 115, 105, 110, 103, 45, 116, 97, 98, 108, 101, 1, 3, 0, 4, 0, 5, 101, 114, 114, 111, 114, 3, 0, 4, 1, 112, 123, 1, 105, 0, 1, 64, 1, 6, 103, 108, 121, 112, 104, 115, 6, 0, 7, 4, 0, 19, 91, 115, 116, 97, 116, 105, 99, 93, 112, 114, 111, 102, 105, 108, 101, 46, 112, 100, 102, 1, 8, 4, 1, 43, 116, 121, 112, 115, 116, 45, 99, 111, 109, 109, 117, 110, 105, 116, 121, 58, 115, 117, 98, 115, 101, 116, 116, 101, 114, 47, 116, 121, 112, 101, 115, 64, 49, 46, 48, 46, 48, 43, 48, 46, 49, 46, 49, 5, 11, 4, 1, 47, 116, 121, 112, 115, 116, 45, 99, 111, 109, 109, 117, 110, 105, 116, 121, 58, 115, 117, 98, 115, 101, 116, 116, 101, 114, 47, 115, 117, 98, 115, 101, 116, 116, 101, 114, 64, 49, 46, 48, 46, 48, 43, 48, 46, 49, 46, 49, 4, 0, 11, 15, 1, 0, 9, 115, 117, 98, 115, 101, 116, 116, 101, 114, 3, 2, 0, 0, 16, 12, 112, 97, 99, 107, 97, 103, 101, 45, 100, 111, 99, 115, 0, 123, 125, 0, 70, 9, 112, 114, 111, 100, 117, 99, 101, 114, 115, 1, 12, 112, 114, 111, 99, 101, 115, 115, 101, 100, 45, 98, 121, 2, 13, 119, 105, 116, 45, 99, 111, 109, 112, 111, 110, 101, 110, 116, 6, 48, 46, 49, 56, 46, 50, 16, 119, 105, 116, 45, 98, 105, 110, 100, 103, 101, 110, 45, 114, 117, 115, 116, 6, 48, 46, 49, 54, 46, 48];

#[inline(never)]
#[doc(hidden)]
#[cfg(target_arch = "wasm32")]
pub fn __link_section() {}

[alexcrichton]

Thanks for the report! It's taken me a bit to get around to this but I can clarify at least that this is expected, albeit I can see surprising, behavior.

This world declaration:

world subsetter {
  export types;
  use types.{profile, tag, error};

  export subset: func(data: list<u8>, index: u32, profile: profile) -> result<list<u8>, error>;
}

elaborates to:

world subsetter {
  import types;
  use types.{profile, tag, error};

  export subset: func(data: list<u8>, index: u32, profile: profile) -> result<list<u8>, error>;

  export types;
}

Top-level functions in a world, like subset, can only access imported types. This means that the profile type, a resource from the types interface, means that the types interface is required to be imported. The world the simultaneously exports the types interface meaning that it both imports and exports the same interface.

Currently there is no means by which a top-level function can access exported types from a world. You'll need to instead wrap the top-level function in its own interface and export that from the world. For example:

package typst-community:subsetter@1.0.0+0.1.1;

interface types {
  resource profile {
    pdf: static func(glyphs: list<u16>) -> profile;
  }

  record tag {
    tuple0: tuple<u8, u8, u8, u8>,
  }

  variant error {
    unknown-kind,
    invalid-offset,
    missing-data,
    invalid-data,
    missing-table(tag),
  }
}

interface subset {
  use types.{profile, tag, error};

  subset: func(data: list<u8>, index: u32, profile: profile) -> result<list<u8>, error>;
}

world subsetter {
  export types;
  export subset;
}

[jcbhmr]

Thank you very much for clarifying how this is being expanded and why this happens. ❤️

Currently there is no means by which a top-level function can access exported types from a world. You'll need to instead wrap the top-level function in its own interface and export that from the world.

Given this fact ☝️ I think that the convention that I was pointed towards in WebAssembly/component-model#295 can be modified slightly:
instead of "functions in top-level world, root-level types in interface types {} (for now until they can be exported on the root)" it should be "everything that would be at the root-level should go in interface types {} (until they can be exported at the root level)" -- is this interpretation accurate?

^{("types" seems to sorta be a catch-all interface since enums/records/resources can't go on the root world similar to default imports in JS. its used by a lot of wasi interfaces from what I've seen)}

or would the idea of a per-function interface work better as shown in the previous comment's example the interface subset {} with the subset() function in it?

[lukewagner]

That all makes sense as what we should say in the short term. Longer-term (w/o saying precisely when), it seems attractive to have a co-expressivity property that everything you can do with imported/exported interfaces one could also do with direct world imports/exports (so that interfaces are only necessary when you want to group/namespace). This seems generally useful for folks hand-authoring component exports (e.g., for library-style components). At the raw C-M level this is the case, so this matches the general WIT/C-M co-expressivity long-term goals.

If we assume that co-expressivity goal, it seems like one should be able to (one day) write, e.g.:

world w {
  export blob-type: resource { ... }
  export make-blob: func() -> blob-type
}

since one could do the same thing inside an export blob: interface { ... }, which implies allowing top-level exported functions to refer to preceding top-level exported types. And then, if we want use directly in a world to match what it means when its inside an exported interface, I think that would imply that the original subsetter example would only have exports, no imports.

Does that sound right, at least as a future goal state?

[alexcrichton]

Yeah sounds good to me! Both using interface types for everything for now for @jcbhmr and in the future being able to export all kinds of things from a world.

I'll note though that this is a bit more subtle than just being able to export types, this is something @lukewagner you and I have talked about in the past but the problem is:

world foo {
    import types;
    export types;

    use type.{a-type}; // does this refer to `import types` or `export types`
}

Right now the answer to the above question is "always import types" but that's a WIT-level limitation rather than a component model limitation. We'll want "power syntax" for resolving that in the future.

[lukewagner]

Hah, yes, that case keeps popping up in my mind too. I expect it'll be rather rare (unlike the common/expected case of importing and exporting the same function-only interface that uses an only-imported type-defining interface), but definitely we need an answer for it.

One idea that could avoid surprise is to say:

• If you write use X.{...} in a world and X has not otherwise been imported or exported, import it.
• If you write use X.{...} in a world and X is already imported xor exported, alias that.
• If you write use X.{...} in a world and X is both imported and exported, syntax error.
• Add new syntax: use import X.{...} or use export X.{...} which aliases the respective import/export if it already exists or adds it if not.

Alternatively, which is technically breaking, but perhaps not yet widely, I was wondering if we maybe want to only allow the final bullet's syntax when inside a world and then then there's never an ambiguity. It also avoids the first bullet's (justified, but still ad hoc) bias towards imports. The different syntax is perhaps justified since worlds inherently have 2 sets whereas interfaces (where use originated) only have 1 set.

[alexcrichton]

That all sounds good to me! I've not given it too much thought before but I like all your recommendations, including requiring the disambiguation by default. I know use has been surprising to folks historically when both imports and exports are in play.

[alexcrichton]

Ok I'm going to close this as expected behavior for now in terms of wit-bindgen, but some of these ideas might be good to move to the component-model repository as well for ideas of future extensions

[lukewagner]

Makes sense. I'll file an issue for use import/use export; that seems like a good (and perhaps short-term) change to make. Achieving general C-M parity is a more open-ended and long-running project, so I'll hold off on filing specific issues there.