Regression building proc-macro2 1.0.59 with nightly-2023-06-28

[davidv1992]

How to fix it:

update proc-macro2 to the latest version.

proc_macro2 1.0.59 Fails to build with nightly-2023-06-28 but succeeds building on nightly-2023-06-27

Code

Create a new binary project with cargo new --bin buildtest

add dependency on proc_macro2 with proc_macro feature:

[dependencies]
proc-macro2 = { version = "=1.0.59", features=["default", "proc-macro"] }

Try building binary with cargo build, it will not work and fail with the following error:

error[E0635]: unknown feature `proc_macro_span_shrink`
  --> /home/david/.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro2-1.0.59/src/lib.rs:92:30
   |
92 |     feature(proc_macro_span, proc_macro_span_shrink)
   |                              ^^^^^^^^^^^^^^^^^^^^^^

For more information about this error, try `rustc --explain E0635`.
error: could not compile `proc-macro2` (lib) due to previous error

Version it worked on

It most recently worked on: nightly-2023-06-27

Version with regression

rustc --version --verbose:

rustc 1.72.0-nightly (5bd28f5ea 2023-06-28)
binary: rustc
commit-hash: 5bd28f5eac1ba3569bfa8d49ec3f5acbdfdff7a0
commit-date: 2023-06-28
host: x86_64-unknown-linux-gnu
release: 1.72.0-nightly
LLVM version: 16.0.5

@rustbot modify labels: +regression-from-stable-to-nightly -regression-untriaged

[Nilstrieb]

#111571 changed the feature gate. proc-macro2 is enabling the nightly feature that doesn't exist anymore. This is an issue with the proc-macro2 crate (cc @dtolnay).

I'm going to leave this issue open for now so that other people can see it.

[Nemo157]

It is fixed in proc-macro2 1.0.60+ dtolnay/proc-macro2#391

[davidv1992]

Good to know it is intended breakage, will upgrade then.