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
* Make ConvertToAst trait fallible
It's got some panics, and we'll be switching those to errors!
* First example of a diagnostic-driven error
Add a diagnostic-driven error `#[wasm_bindgen]` being attached to public
functions, and add some macros to boot to make it easier to generate errors!
* Result-ify `src/parser.rs`
This commit converts all of `src/parser.rs` away from panics to using
`Diagnostic` instead. Along the way this adds a test case per changed `panic!`,
ensuring that we don't regress in these areas!
