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)

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.

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.

@jyn514

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

@Wardenfar

@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 :)

@jyn514

@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() {}
```

@Wardenfar

@Wardenfar you can use normalize-stderr-test: https://rustc-dev-guide.rust-lang.org/tests/adding.html#output-normalization. But I'm surprised $DIR doesn't work :/ that does seem like a bug.

@jyn514

Sorry I was not clear : the $DIR is working for the test.stderr
But the path is not replace for the error comment in the test.rs because the path read by include_str is in the error message
@jyn514

@Wardenfar

@Wardenfar don't put the whole name in the .rs file - you just need to put a substring. Something like //~^^ ERROR No such file or directory.

Rollup merge of rust-lang#89023 - Wardenfar:issue-85066, r=nagisa

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Somewhat confusing error with `extended_key_value_attributes` #85066

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Somewhat confusing error with extended_key_value_attributes #85066

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camelid commented on May 25, 2021

jyn514 commented on Sep 16, 2021

Wardenfar commented on Sep 16, 2021

jyn514 commented on Sep 16, 2021

Wardenfar commented on Sep 16, 2021

jyn514 commented on Sep 16, 2021

Wardenfar commented on Sep 16, 2021

jyn514 commented on Sep 16, 2021

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Somewhat confusing error with `extended_key_value_attributes` #85066