Somewhat confusing error with `extended_key_value_attributes`

[camelid]

Code

Note that ../README.md must not exist in order to reproduce this error:

#![feature(extended_key_value_attributes)]
#![doc = include_str!("../README.md")]

Playground

Output

The first error is what I would expect, but the second is a bit confusing and weird:

error: couldn't read src/../README.md: No such file or directory (os error 2)
 --> src/lib.rs:2:10
  |
2 | #![doc = include_str!("../README.md")]
  |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: unexpected token: `(/*ERROR*/)`
 --> src/lib.rs:2:10
  |
2 | #![doc = include_str!("../README.md")]
  |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 2 previous errors

Perhaps instead of emitting unexpected token: `(/*ERROR*/)` when an error token is encountered, we could use a delay_span_bug since an error should have already occurred.

If for some reason an error had not already been emitted, the compiler would crash; otherwise, it would just show the original error.

Originally posted by @camelid in #83366 (comment)

[camelid]

Note that extended_key_value_attributes is stable now (though it hasn't reached the stable channel yet), so this no longer requires a feature flag.

[jyn514]

Mentoring instructions: in

rust/compiler/rustc_parse/src/parser/expr.rs

Line 1496 in 34327f6

let msg = format!("unexpected token: {}", super::token_descr(&self.token));

, check if the token is a token::Interpolated(token::NtExpr(expr) | NtLiteral(expr)) and the expression is an error; if so, use delay_span_bug instead of struct_span_err.

[Wardenfar]

Hi @jyn514
I was searching for a first issue and i have a question :
What does delay_span_bug ? Because the function that you pin must return a PResult but delay_span_bug has return type ()
Sorry if i misread something

[jyn514]

@Wardenfar delay_span_bug means "if the compiler finishes running without first reporting another error, panic". It's useful here because error tokens should always report in an error being reported.

I think anything you return is probably fine as long as it doesn't cause further cascading errors :)

[Wardenfar]

@jyn514 i fixed it but for adding a test case : i run into an edge case
the output message of the macro : include_str! is not normalized with $DIR
the ui test is working only for me. Have you a tip or i have to create an issue ?
Thanks

#![feature(extended_key_value_attributes)]
#![doc = include_str!("../not_existing_file.md")]
struct Documented {}
//~^^ ERROR 2:10: 2:49: couldn't read /home/<username>/dev/rustc/rust/src/test/ui/attributes/../not_existing_file.md: No such file or directory (os error 2)

fn main() {}
```