Regression in 1.62.0 with macro exports in doctests

[jonhoo]

Code

I tried this code (in a crate called foo):

/// ```
/// # #[macro_use] extern crate foo;
///
/// mockable! {}
/// ```
macro_rules! mockable {
    () => {};
}

and run

$ cargo t --doc

I expected to see this happen: the doctest passes

Instead, this happened: the doctest fails to build with

running 1 test
test src/lib.rs - mockable (line 1) ... FAILED

failures:

---- src/lib.rs - mockable (line 1) stdout ----
error: cannot find macro `mockable` in this scope
 --> src/lib.rs:4:1
  |
5 | mockable! {}
  | ^^^^^^^^

error: aborting due to previous error

Version it worked on

It most recently worked on: Rust 1.61.0

Version with regression

rustc --version --verbose:

rustc 1.62.0 (a8314ef7d 2022-06-27)
binary: rustc
commit-hash: a8314ef7d0ec7b75c336af2c9857bfaf43002bfc
commit-date: 2022-06-27
host: aarch64-unknown-linux-gnu
release: 1.62.0
LLVM version: 14.0.5

Notes

It works if I add #[macro_export] above the macro_rules!. If intended, this feels like it should be listed in the compatibility notes.

[steffahn]

On my machine, on 1.61 or older it doesn’t appear to be running the doctest at all (i.e. it says running 0 tests, and the test could just as well be completely invalid code, or unconditionally failing); does that mirror what you’re observing?

[jonhoo]

Oh, yes, good catch, that's what I observe on 1.61 and before too.

[jonhoo]

Makes me wonder if this is somehow related to rust-lang/cargo#10594

[steffahn]

Running cargo-bisect-rustc…

regressed nightly: nightly-2022-05-06
searched commit range: 4c60a0e...30f3860
regressed commit: 3d18f94

which is #96630 which has a relnotes tag, and is considered a bugfix (of #88038). I don’t know why it didn’t actually end up in the release notes, as far as I can tell.

[jyn514]

Duplicate of #97030

[jonhoo]

@jyn514 I left a comment over there. I think we should make sure to update the changelog with a note about this change then, and sooner rather than later since 1.62.0 is now out.

[jyn514]

I'm not the one who approved the PR. Anyone is welcome to submit a change to the release notes.