parse_item panics when given an incomplete impl trait block

[lilizoey]

If you try to use parse_item on an impl trait block like this:

#[some_macro]
impl SomeTrait for Foo {
    fn re
}

Then venial will panic because of a call to Option::unwrap. I believe it is this call specifically.

This is a problem as a proc-macro panicking like this prevents RA from reliably autocompleting the code.

[PoignardAzur]

I'd honestly say this is a problem with RA and not this macro? If the block is invalid, then it shouldn't be fed to venial in the first place.

Making venial resilient to parsing errors would be a pretty deep change, much deeper than I'm willing to do.

[dtolnay]

This was the upstream rust-analyzer bug. rust-lang/rust-analyzer#10468 (comment)

But I thought it got fixed as part of rust-lang/rust-analyzer#11014. Is the repro here really an attribute macro or were you using venial from a bang macro?

[PoignardAzur]

Wasn't expecting to see a reply from you. Out of curiosity, how did you get pinged about this?

[lilizoey]

This was the upstream rust-analyzer bug. rust-lang/rust-analyzer#10468 (comment)

But I thought it got fixed as part of rust-lang/rust-analyzer#11014. Is the repro here really an attribute macro or were you using venial from a bang macro?

It sometimes works but very unreliably when the attribute macro panics. I've got it to autocomplete a function name, but also sometimes it just doesn't work at all. i'll see if i can make a smaller repro since i've been using a much bigger more complicated attribute macro, however the panic is what it complained about.

[lilizoey]

Yes, using this proc macro code:

use proc_macro::TokenStream;

#[proc_macro_attribute]
pub fn some_macro(_attr: TokenStream, _item: TokenStream) -> TokenStream {
    panic!("i failed!");
}

and this code:

use fucky_macros::some_macro;

pub trait Foo {
    fn my_function() {}
}

pub struct Bar;

#[some_macro]
impl Foo for Bar {
    fn m
}

the autocompletion fails:

well in this case the correct function name shows up, but i'd expect the output that happens without the macro at all:

and it does work when i replace the proc-macro with a noop like:

#[proc_macro_attribute]
pub fn some_macro(_attr: TokenStream, _item: TokenStream) -> TokenStream {
    // panic!("i failed!");
    _item
}

in fact when the attribute macro panics, and i write fn i get this autocompletion:

which seems strange

this is all with RA version v0.3.2220. the current pre-release gives the weird output with a noop attribute proc-macro too.