expected unsuffixed literal or identifier, found `IN_ISDIR`

[Thomasdezeeuw]

I have the following (open source) code: https://github.com/Thomasdezeeuw/heph/blob/1c7ee4af37627fcfb11749389973fa5e4a34a0bf/rt/src/fs/watch.rs#L354-L466. It's over a 100 lines and I'm not sure what is causing the issue.

This compiled fine since it was added to the repository, latest nightly compiler that is know to work is from rustc 1.78.0-nightly (c67326b06 2024-03-15).

However using the currently nightly compiler, 1.79.0-nightly (a7e4de13c 2024-03-19), fails to compile it giving the following errors:

Details

error: expected unsuffixed literal or identifier, found `IN_ISDIR`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_ACCESS`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_MODIFY`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_ATTRIB`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_CLOSE_WRITE`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_CLOSE_NOWRITE`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_CLOSE`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_OPEN`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_DELETE_SELF`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_MOVE_SELF`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_UNMOUNT`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_MOVED_FROM`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_MOVED_TO`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_MOVE`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_CREATE`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `IN_DELETE`
   --> rt/src/fs/watch.rs:454:23
    |
354 |     bit_checks!(self.event.mask);
    |     ---------------------------- in this macro invocation
...
454 |         #[doc(alias = $bit)]
    |                       ^^^^
    |
    = note: this error originates in the macro `bit_checks` (in Nightly builds, run with -Z macro-backtrace for more info)

error: could not compile `heph-rt` (lib) due to 16 previous errors
make: *** [Makefile.include:21: test] Error 101

Also available on the CI:

• with Clippy: https://github.com/Thomasdezeeuw/heph/actions/runs/8366117475/job/22905578987?pr=617#step:4:59,
• with rustdoc: https://github.com/Thomasdezeeuw/heph/actions/runs/8366117475/job/22905579591?pr=617#step:4:132

There are two problems. First, the regression from the previous nightly. Second, the error message is rather confusing, I have would have no idea what the actual problem is.

Meta

rustc --version --verbose:

rustc 1.79.0-nightly (a7e4de13c 2024-03-19)
binary: rustc
commit-hash: a7e4de13c1785819f4d61da41f6704ed69d5f203
commit-date: 2024-03-19
host: x86_64-unknown-linux-gnu
release: 1.79.0-nightly
LLVM version: 18.1.2

[Thomasdezeeuw]

The code works with nightly-2024-03-16:

rustc 1.78.0-nightly (766bdce74 2024-03-16)
binary: rustc
commit-hash: 766bdce744d531267d53ba2a3f9ffcda69fb9b17
commit-date: 2024-03-16
host: x86_64-unknown-linux-gnu
release: 1.78.0-nightly
LLVM version: 18.1.2

[jieyouxu]

Exhibit A:

#![crate_type = "lib"]
#![allow(dead_code)]

pub const IN_ISDIR: usize = 0;

macro_rules! m {
    ($bit: ident) => {
        #[doc(alias = $bit)]
        pub const fn foo() {}
    };
}

struct Bar;

impl Bar {
    m!(IN_ISDIR);
}

OK on stable, ERROR on nightly 2024-03-19.

---

Exhibit B:

#![crate_type = "lib"]
#![allow(dead_code)]

pub const IN_ISDIR: usize = 0;

macro_rules! m {
    ($bit: ident) => {
        #[doc(alias = $bit)]
        pub const fn foo() {}
    };
}

struct Bar;

m!(IN_ISDIR);

ERROR on both.

---

Exhibit C:

#![crate_type = "lib"]
#![allow(dead_code)]

pub const IN_ISDIR: usize = 0;

macro_rules! m {
    ($bit: ident) => {
        #[doc(alias = $bit)]
        pub fn foo() {}            // <- notice not `const` like Exhibit A
    };
}

struct Bar;

impl Bar {
    m!(IN_ISDIR);
}

ERROR on both.

[fmease]

First and foremost, sorry for breaking your crate! However this was an intentional breaking change. We used to not validate attributes on certain kinds of associated functions. We did a crater run and found only a single regression. Therefore I decided to roll with it.

[fmease]

Intentionally regressed in #121545.

[jieyouxu]

Makes a lot of sense, was about to say the stable behavior is the surprising one lol

[fmease]

@Thomasdezeeuw Your #[doc(alias = $bit)] attribute is malformed, the latest rustc is correct here. The doc-alias takes a string literal IIRC. To fix this, you can do #[doc(alias = stringify!($bit))].

See also: https://doc.rust-lang.org/rustdoc/advanced-features.html#add-aliases-for-an-item-in-documentation-search

[jieyouxu]

Intentionally regressed in #121545.

If this is an intentional regression, we can probably close this issue?