wasm-bindgen/crates/macro/ui-tests/unused-attributes.rs
Alex Crichton c35d6f4b0a Fix conditional #[wasm_bindgen] in impls
Reported in #1191 the fix requires us to get a bit creative I think. The
general gist is that a block like this:

    #[wasm_bindgen]
    impl Foo {
        pub fn foo() {}
    }

was previously expanded all in one go. Now, however, it's expanded into:

    impl Foo {
        #[__wasm_bindgen_class_marker(Foo = "Foo")]
        pub fn foo() {}
    }

    // goop generated by orginal #[wasm_bindgen]

This method of expansion takes advantage of rustc's recursive expansion
feature. It also allows us to expand `impl` blocks and allow inner items
to not be fully expanded yet, such as still having `#[cfg]` attributes
(like in the original bug report).

We use theinternal `__wasm_bindgen_class_marker` to indicate that we're
parsing an `ImplItemMethod` unconditionally, and then generation
proceeds as usual. The only final catch is that when we're expanding in
an `impl` block we have to generate tokens for the `Program`
(wasm-bindgen injected goop like the custom section) inside the body
of the function itself instead of next to it. Otherwise we'd get syntax
errors inside of impl blocks!

Closes #1191
2019-01-28 12:29:01 -08:00

16 lines
203 B
Rust

#![crate_type = "rlib"]
extern crate wasm_bindgen;
use wasm_bindgen::prelude::*;
struct A;
#[wasm_bindgen]
impl A {
#[wasm_bindgen(method)]
#[wasm_bindgen(method)]
pub fn foo() {
}
}