traits of a wasm_bindgen type

[nearest-river]

what are the traits that the wasm_bindgen impls for a type.

Example

#[wasm_bindgen]
struct Foo {
    foo: Vec<u8>
}

the intellisence says that it has 12 implementations but doesn't show the traits

[Liamolucko]

You can find out by using cargo-expand to see the code that wasm-bindgen generates. This is what cargo expand --target wasm32-unknown-unknown prints out for your example:

#![feature(prelude_import)]
#[prelude_import]
use std::prelude::rust_2021::*;
#[macro_use]
extern crate std;
use wasm_bindgen::prelude::*;
struct Foo {
    foo: Vec<u8>,
}
#[automatically_derived]
impl wasm_bindgen::describe::WasmDescribe for Foo {
    fn describe() {
        use wasm_bindgen::__wbindgen_if_not_std;
        use wasm_bindgen::describe::*;
        inform(RUST_STRUCT);
        inform(3u32);
        inform(70u32);
        inform(111u32);
        inform(111u32);
    }
}
#[automatically_derived]
impl wasm_bindgen::convert::IntoWasmAbi for Foo {
    type Abi = u32;
    fn into_abi(self) -> u32 {
        use wasm_bindgen::__rt::std::boxed::Box;
        use wasm_bindgen::__rt::WasmRefCell;
        Box::into_raw(Box::new(WasmRefCell::new(self))) as u32
    }
}
#[automatically_derived]
impl wasm_bindgen::convert::FromWasmAbi for Foo {
    type Abi = u32;
    unsafe fn from_abi(js: u32) -> Self {
        use wasm_bindgen::__rt::std::boxed::Box;
        use wasm_bindgen::__rt::{assert_not_null, WasmRefCell};
        let ptr = js as *mut WasmRefCell<Foo>;
        assert_not_null(ptr);
        let js = Box::from_raw(ptr);
        (*js).borrow_mut();
        js.into_inner()
    }
}
#[automatically_derived]
impl wasm_bindgen::__rt::core::convert::From<Foo> for wasm_bindgen::JsValue {
    fn from(value: Foo) -> Self {
        let ptr = wasm_bindgen::convert::IntoWasmAbi::into_abi(value);
        #[link(wasm_import_module = "__wbindgen_placeholder__")]
        #[cfg(
            all(
                target_arch = "wasm32",
                not(any(target_os = "emscripten", target_os = "wasi"))
            )
        )]
        extern "C" {
            fn __wbg_foo_new(ptr: u32) -> u32;
        }
        unsafe {
            <wasm_bindgen::JsValue as wasm_bindgen::convert::FromWasmAbi>::from_abi(
                __wbg_foo_new(ptr),
            )
        }
    }
}
#[cfg(
    all(target_arch = "wasm32", not(any(target_os = "emscripten", target_os = "wasi")))
)]
#[automatically_derived]
const _: () = {
    #[no_mangle]
    #[doc(hidden)]
    pub unsafe extern "C" fn __wbg_foo_free(ptr: u32) {
        let _ = <Foo as wasm_bindgen::convert::FromWasmAbi>::from_abi(ptr);
    }
};
#[automatically_derived]
impl wasm_bindgen::convert::RefFromWasmAbi for Foo {
    type Abi = u32;
    type Anchor = wasm_bindgen::__rt::Ref<'static, Foo>;
    unsafe fn ref_from_abi(js: Self::Abi) -> Self::Anchor {
        let js = js as *mut wasm_bindgen::__rt::WasmRefCell<Foo>;
        wasm_bindgen::__rt::assert_not_null(js);
        (*js).borrow()
    }
}
#[automatically_derived]
impl wasm_bindgen::convert::RefMutFromWasmAbi for Foo {
    type Abi = u32;
    type Anchor = wasm_bindgen::__rt::RefMut<'static, Foo>;
    unsafe fn ref_mut_from_abi(js: Self::Abi) -> Self::Anchor {
        let js = js as *mut wasm_bindgen::__rt::WasmRefCell<Foo>;
        wasm_bindgen::__rt::assert_not_null(js);
        (*js).borrow_mut()
    }
}
#[automatically_derived]
impl wasm_bindgen::convert::LongRefFromWasmAbi for Foo {
    type Abi = u32;
    type Anchor = wasm_bindgen::__rt::Ref<'static, Foo>;
    unsafe fn long_ref_from_abi(js: Self::Abi) -> Self::Anchor {
        <Self as wasm_bindgen::convert::RefFromWasmAbi>::ref_from_abi(js)
    }
}
#[automatically_derived]
impl wasm_bindgen::convert::OptionIntoWasmAbi for Foo {
    #[inline]
    fn none() -> Self::Abi {
        0
    }
}
#[automatically_derived]
impl wasm_bindgen::convert::OptionFromWasmAbi for Foo {
    #[inline]
    fn is_none(abi: &Self::Abi) -> bool {
        *abi == 0
    }
}
#[allow(clippy::all)]
impl wasm_bindgen::__rt::core::convert::TryFrom<wasm_bindgen::JsValue> for Foo {
    type Error = wasm_bindgen::JsValue;
    fn try_from(
        value: wasm_bindgen::JsValue,
    ) -> wasm_bindgen::__rt::std::result::Result<Self, Self::Error> {
        let idx = wasm_bindgen::convert::IntoWasmAbi::into_abi(&value);
        #[link(wasm_import_module = "__wbindgen_placeholder__")]
        #[cfg(
            all(
                target_arch = "wasm32",
                not(any(target_os = "emscripten", target_os = "wasi"))
            )
        )]
        extern "C" {
            fn __wbg_foo_unwrap(ptr: u32) -> u32;
        }
        let ptr = unsafe { __wbg_foo_unwrap(idx) };
        if ptr == 0 {
            wasm_bindgen::__rt::std::result::Result::Err(value)
        } else {
            wasm_bindgen::__rt::std::mem::forget(value);
            unsafe {
                wasm_bindgen::__rt::std::result::Result::Ok(
                    <Self as wasm_bindgen::convert::FromWasmAbi>::from_abi(ptr),
                )
            }
        }
    }
}
impl wasm_bindgen::describe::WasmDescribeVector for Foo {
    fn describe_vector() {
        use wasm_bindgen::describe::*;
        inform(VECTOR);
        inform(NAMED_EXTERNREF);
        inform(3u32);
        inform(70u32);
        inform(111u32);
        inform(111u32);
    }
}
impl wasm_bindgen::convert::VectorIntoWasmAbi for Foo {
    type Abi = <wasm_bindgen::__rt::std::boxed::Box<
        [wasm_bindgen::JsValue],
    > as wasm_bindgen::convert::IntoWasmAbi>::Abi;
    fn vector_into_abi(vector: wasm_bindgen::__rt::std::boxed::Box<[Foo]>) -> Self::Abi {
        wasm_bindgen::convert::js_value_vector_into_abi(vector)
    }
}
impl wasm_bindgen::convert::VectorFromWasmAbi for Foo {
    type Abi = <wasm_bindgen::__rt::std::boxed::Box<
        [wasm_bindgen::JsValue],
    > as wasm_bindgen::convert::FromWasmAbi>::Abi;
    unsafe fn vector_from_abi(
        js: Self::Abi,
    ) -> wasm_bindgen::__rt::std::boxed::Box<[Foo]> {
        wasm_bindgen::convert::js_value_vector_from_abi(js)
    }
}
#[cfg(target_arch = "wasm32")]
#[automatically_derived]
const _: () = {
    static _INCLUDED_FILES: &[&str] = &[];
    #[link_section = "__wasm_bindgen_unstable"]
    pub static _GENERATED: [u8; 112usize] = *b".\x00\x00\x00{\"schema_version\":\"0.2.88\",\"version\":\"0.2.88\"}:\x00\x00\x00\x00\x00\x00\x01\x03Foo\x00\x00\x00\x01\x00\x00\x00(wasm-bindgen-playground-db5fbe5f033bb9af\x00\x00";
};

Most of them are internal to wasm-bindgen. The only ones which aren't are the From<Foo> for JsValue and TryFrom<JsValue> for Foo implementations (the From<Foo> for JsValue impl isn't actually included in the 12 since it's technically implementing a trait for JsValue).

Another solution would be running cargo doc on your crate. All the traits that Foo implements should then be listed on its page. It might not include the From<Foo> for JsValue impl though.