rust: async function failed to compile with `wit-bindgen` 0.48.0

[crlcrl1]

Async functions fail to compile with wit-bindgen==0.48.0, but works fine with wit-bindgen==0.47.0. Here is a minimal reproduce:

Cargo.toml:

[package]
name = "wit-test"
version = "0.1.0"
edition = "2024"

[lib]
crate-type = ["cdylib"]

[dependencies]
wit-bindgen = "xxx" # change this to 0.47.0 or 0.48.0

wit/adder/world.wit:

package docs:adder@0.1.0;

interface add {
    add: async func(a: u32, b: u32) -> u32;
}

world adder {
    export add;
}

src/lib.rs

use crate::bindings::exports::docs::adder::add::Guest;

mod bindings {
    wit_bindgen::generate!({
        path: "wit/adder/world.wit",
    });

    use super::AdderComponent;
    export!(AdderComponent);
}

struct AdderComponent;

impl Guest for AdderComponent {
    async fn add(a: u32, b: u32) -> u32 {
        a + b
    }
}

I compile it with cargo build --target wasm32-wasip2. Here is the compiler output:

error: linking with `wasm-component-ld` failed: exit status: 1
  |
  = note:  "wasm-component-ld" "-flavor" "wasm" "--export" "[async-lift]docs:adder/add@0.1.0#add" "--export" "[callback][async-lift]docs:adder/add@0.1.0#add" "--export" "cabi_realloc" "-z" "stack-size=1048576" "--stack-first" "--allow-undefined" "--no-demangle" "<15 object files omitted>" "<sysroot>/lib/rustlib/wasm32-wasip2/lib/libpanic_abort-*.rlib" "/home/crl/code/rust/wit-test/target/wasm32-wasip2/debug/deps/{libwit_bindgen-918753b0b2fdee64,libbitflags-d3add546d7ca84d2}.rlib" "<sysroot>/lib/rustlib/wasm32-wasip2/lib/{libstd-*,libwasi-*,libwasi-*,libwit_bindgen-*,libcfg_if-*,librustc_demangle-*,libstd_detect-*,libhashbrown-*,librustc_std_workspace_alloc-*,libminiz_oxide-*,libadler2-*,libunwind-*,liblibc-*}.rlib" "-l" "c" "<sysroot>/lib/rustlib/wasm32-wasip2/lib/{librustc_std_workspace_core-*,liballoc-*,libcore-*,libcompiler_builtins-*}.rlib" "-L" "/home/crl/code/rust/wit-test/target/wasm32-wasip2/debug/build/wit-bindgen-5be24b2b4ddface3/out" "-L" "<sysroot>/lib/rustlib/wasm32-wasip2/lib/self-contained" "-o" "/home/crl/code/rust/wit-test/target/wasm32-wasip2/debug/deps/wit_test.wasm" "--gc-sections" "--no-entry" "-O0"
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: error: failed to parse core wasm for componentization
          
          Caused by:
              0: decoding custom section component-type:wit-bindgen:0.48.0:docs:adder@0.1.0:adder:encoded world
              1: invalid leading byte (0x43) for component defined type (at offset 0x2f)

My rust version is 1.91.1

[crlcrl1]

In addition, if I use wasm-component-ld 0.5.19 and wit-bindgen 0.48.0, it works. But with wasm-component-ld 0.5.17 (bundled version with rust toolchain), it doesn't compile

[alexcrichton]

Thanks for the report! This is however an expected change and is a result of bytecodealliance/wasm-tools#2376. There will be a bit of a transition period where tools need to precolate to pick up this change, and for now you'll need to use nightly Rust to compile p3 modules or pass the -Clink-arg=--skip-wit-component option and run wasm-tools component new manually. There should be a component-model-side PR shortly to point to as well.