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wit-bindgen panics on import + async + sized lists #1744
Description
I continue hacking on Brevity and ran into a case where wit-bindgen’s Rust macro panics.
Here’s a little .wit declaration that imports an async function that accepts a sized list as a parameter.
package brevity:testing;
world brevity-test {
import import-sized-list: async func(v: list<bool,2>) -> s32;
export export-sized-list: async func(v: list<bool>) -> s32;
}Here’s Rust that implements the guest side:
#![allow(unused_imports)]
use std::thread::sleep;
use std::time::Duration;
mod bindings {
wit_bindgen::generate!({
path: "./wit/sizedlists.wit",
});
use super::BrevityTesting;
export!(BrevityTesting);
}
struct BrevityTesting;
impl bindings::Guest for BrevityTesting {
async fn export_sized_list(_v: Vec<bool>) -> i32 {
0
}
}Here’s the obvious cargo.toml:
[package]
name = "brevity-testing-sizedLists"
version = "0.1.0"
edition = "2024"
[dependencies]
wit-bindgen = "0.62.0"
[lib]
path = "src/sizedLists_lib.rs"
crate-type = ['cdylib']Expected
Program compiles
Actual
Macro panics.
$ cargo build --target=wasm32-wasip2 --release
Compiling brevity-testing-sizedLists v0.1.0 (/Volumes/Development/brevity/brevity-integration-tests/build/BrevityExecutionTester/sizedLists/rust)
error: proc macro panicked
--> src/sizedLists_lib.rs:6:5
|
6 | / wit_bindgen::generate!({
7 | | path: "./wit/sizedlists.wit",
8 | | });
| |______^
|
= help: message: not yet implemented
error: cannot find macro `export` in this scope
--> src/sizedLists_lib.rs:11:5
|
11 | export!(BrevityTesting);
| ^^^^^^
error[E0405]: cannot find trait `Guest` in module `bindings`
--> src/sizedLists_lib.rs:16:16
|
16 | impl bindings::Guest for BrevityTesting {
| ^^^^^ not found in `bindings`
For more information about this error, try `rustc --explain E0405`.
error: could not compile `brevity-testing-sizedLists` (lib) due to 3 previous errors
Work-around by editing the wit to not use a sized list.
package brevity:testing;
world brevity-test {
- import import-sized-list: async func(v: list<bool,2>) -> s32;
+ import import-sized-list: async func(v: list<bool>) -> s32;
export export-sized-list: async func(v: list<bool>) -> s32;
}This isn’t blocking us. Thanks!
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