Regression in binary_macros-0.6.3, Rust 1.16

[brson]

101 brian@ip-10-145-43-250:~/dev/binary_macros⟫ git remote -v
origin  https://github.com/golddranks/binary_macros (fetch)
origin  https://github.com/golddranks/binary_macros (push)
brian@ip-10-145-43-250:~/dev/binary_macros⟫ git log -1
commit 04008be68f8d71e8684c050d540c743eb50e5124
Author: Pyry Kontio <pyry.kontio@drasa.eu>
Date:   Fri Mar 3 14:49:04 2017 +0200

    Trying to get categories to work. 0.6.3

brian@ip-10-145-43-250:/mnt2/dev⟫ rustc +beta -Vv
rustc 1.16.0-beta.3 (ecbf0b59e 2017-03-02)
binary: rustc
commit-hash: ecbf0b59e409af1a09c1c7c3947858c5e78f416d
commit-date: 2017-03-02
host: x86_64-unknown-linux-gnu
release: 1.16.0-beta.3
LLVM version: 3.9

error: attempted to repeat an expression containing no syntax variables matched as repeating at this depth
  --> src/lib.rs:25:1
   |
25 | proc_macro_expr_decl!(base64_nopad! => base64_nopad_impl);
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in a macro outside of the current crate

error: attempted to repeat an expression containing no syntax variables matched as repeating at this depth
  --> src/lib.rs:25:1
   |
25 | proc_macro_expr_decl!(base64_nopad! => base64_nopad_impl);
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in a macro outside of the current crate

error: attempted to repeat an expression containing no syntax variables matched as repeating at this depth
  --> src/lib.rs:26:1
   |
26 | proc_macro_expr_decl!(base64url_nopad! => base64url_nopad_impl);
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in a macro outside of the current crate

error: attempted to repeat an expression containing no syntax variables matched as repeating at this depth
  --> src/lib.rs:26:1
   |
26 | proc_macro_expr_decl!(base64url_nopad! => base64url_nopad_impl);
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in a macro outside of the current crate

Not on 1.15. Not on 1.17 nightly

cc @jseyfried can you think of a backport that will fix this?

cc @golddranks

[golddranks]

Are other crates that depend on proc-macro-hack unaffected?

[golddranks]

Ah, I think that this was documented by @dtolnay; it used to affect nightlies.

https://github.com/dtolnay/proc-macro-hack

Note: Requires stable Rust 1.15, beta Rust 1.16, or nightly Rust 1.17 with a date 2017-03-01 or later due to a regression affecting earlier 1.17 nightlies (#39889).

[golddranks]

At least the symptoms are the same, as far as I can remember. Was there some other backports from nightly that triggered this on beta? It was this: #39419 that eventually fixed this, if this bug is what I think it is.

[dtolnay]

This definitely used to work on 1.16.0-beta so it must have been triggered by a backport.

EDIT: Works on rustc 1.16.0-beta.2 (bc15d52 2017-02-16) which rustup calls beta-2017-02-17. Does not work on rustc 1.16.0-beta.3 (ecbf0b5 2017-03-02) which rustup calls beta-2017-03-03.

[nikomatsakis]

@jseyfried do you have any idea what is the problem here? this really needs to be fixed in next 72 hours or so if we are to prepare the stable release.

[brson]

Let's verify that it worked on previous betas, then try to bisect the backports.

[jseyfried]

This was caused by #39730 -- I'll fix today.

[jseyfried]

Fixed in #40411.