[Macro expansion] "failed to process buffered lint"

[ZippyMagician]

Code

After testing, it's this macro here:

macro_rules! len {
    () => { 0 };
    ($item:literal) => { 1 };
    ($item:literal, $($extras:literal),*) => { 1 + len!($($extras),*); }
}

The semicolon in the third variant causes the error when used in a context such as:

macro_rules! operators {
    ($($chr:literal : $prec:literal; $left_rank:literal - $right_rank:literal),*) => {
        ...
            pub operators: [String; len!($($chr),*)] // This line here
        ...
    };
}

Meta

Note that prior to updating I was using 1.49.0, which did not error.
This errors on Nightly and Stable, I tested both (cargo +nightly check and cargo check both have the same result). Removing the semicolon causes the project to build fine and function as it did before updating.

rustc --version --verbose:

rustc 1.51.0 (2fd73fabe 2021-03-23)
binary: rustc
commit-hash: 2fd73fabe469357a12c2c974c140f67e7cdd76d0
commit-date: 2021-03-23
host: x86_64-unknown-linux-gnu
release: 1.51.0
LLVM version: 11.0.1

Error output

This error is repeated over and over again before the notification saying to submit the bug report

error: internal compiler error: failed to process buffered lint here
  --> src/utils/consts.rs:39:70
   |
39 |       ($item:literal, $($extras:literal),*) => { 1 + len!($($extras),*); }
   |                                                                        ^
...
73 | / operators! {
74 | |     '.': 11; 1-1,
75 | |     '^': 10; 1-1,
76 | |     '*': 9; 1-1, '/': 9; 1-1,
...  |
88 | |     ':': 0; 1-1
89 | | }
   | |_- in this macro invocation
   |
   = note: delayed at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/compiler/rustc_lint/src/early.rs:393:18
   = note: this error: internal compiler error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

Backtrace

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', compiler/rustc_errors/src/lib.rs:1018:13
stack backtrace:
   0:     0x7f8da84d6320 - std::backtrace_rs::backtrace::libunwind::trace::hdcf4f90f85129e83
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/../../backtrace/src/backtrace/libunwind.rs:90:5
   1:     0x7f8da84d6320 - std::backtrace_rs::backtrace::trace_unsynchronized::h2669e30cb82f6732
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f8da84d6320 - std::sys_common::backtrace::_print_fmt::hfbda19e17f6db318
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7f8da84d6320 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1a8751bf59281272
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x7f8da854767f - core::fmt::write::h7aa6cd0067dca82a
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/core/src/fmt/mod.rs:1094:17
   5:     0x7f8da84cab45 - std::io::Write::write_fmt::hd7dd3a1df9b6befb
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/io/mod.rs:1580:15
   6:     0x7f8da84d9f0b - std::sys_common::backtrace::_print::h551e9ec8a9fa8106
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/sys_common/backtrace.rs:49:5
   7:     0x7f8da84d9f0b - std::sys_common::backtrace::print::ha4b1c5e95fa040b3
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/sys_common/backtrace.rs:36:9
   8:     0x7f8da84d9f0b - std::panicking::default_hook::{{closure}}::h0b34c9ab7fb9f857
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/panicking.rs:208:50
   9:     0x7f8da84d99ed - std::panicking::default_hook::h3067e8318decd17a
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/panicking.rs:225:9
  10:     0x7f8da8c9bd4d - rustc_driver::report_ice::h0582ed2432eb0d01
  11:     0x7f8da84da620 - std::panicking::rust_panic_with_hook::h81b8facc50f34daa
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/panicking.rs:595:17
  12:     0x7f8da84da1f7 - std::panicking::begin_panic_handler::{{closure}}::ha376ab85d95a000e
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/panicking.rs:497:13
  13:     0x7f8da84d67dc - std::sys_common::backtrace::__rust_end_short_backtrace::h6795c8afdd1a77e6
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/sys_common/backtrace.rs:141:18
  14:     0x7f8da84da159 - rust_begin_unwind
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/panicking.rs:493:5
  15:     0x7f8da84a607b - std::panicking::begin_panic_fmt::hf43a0025042538e2
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/panicking.rs:435:5
  16:     0x7f8dab1066e9 - rustc_errors::HandlerInner::flush_delayed::ha043eb844eec51b4
  17:     0x7f8dab1051db - <rustc_errors::HandlerInner as core::ops::drop::Drop>::drop::h20e6dc4c247e2972
  18:     0x7f8daa77faa6 - core::ptr::drop_in_place<rustc_session::parse::ParseSess>::ha7b7bc007b685a43
  19:     0x7f8daa78e341 - <alloc::rc::Rc<T> as core::ops::drop::Drop>::drop::h0df1456cb7f7b3c5
  20:     0x7f8daa7747ed - core::ptr::drop_in_place<rustc_interface::interface::Compiler>::h4b05c244ac5fa340
  21:     0x7f8daa7740ed - rustc_span::with_source_map::h67cb68e15a9ffc39
  22:     0x7f8daa775f31 - rustc_interface::interface::create_compiler_and_run::he6a465670788f848
  23:     0x7f8daa78f6b8 - scoped_tls::ScopedKey<T>::set::h8de4c07d6e313e7a
  24:     0x7f8daa78fbd3 - std::sys_common::backtrace::__rust_begin_short_backtrace::h953d4096b984a1d5
  25:     0x7f8daa793505 - core::ops::function::FnOnce::call_once{{vtable.shim}}::hf2d8af4e3cccbbb1
  26:     0x7f8da84ea513 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h3aa31cb6360b59d9
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/alloc/src/boxed.rs:1546:9
  27:     0x7f8da84ea513 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h7719d3c7c5841461
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/alloc/src/boxed.rs:1546:9
  28:     0x7f8da84ea513 - std::sys::unix::thread::Thread::new::thread_start::hfbe13ead469fd0bc
                               at /rustc/132b4e5d167b7e622fcc11fa2b67b931105b4de1/library/std/src/sys/unix/thread.rs:71:17
  29:     0x7f8da8415609 - start_thread
  30:     0x7f8da8329293 - clone
  31:                0x0 - <unknown>

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.53.0-nightly (132b4e5d1 2021-04-13) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack

[apiraino]

Assigning priority as discussed as part of the Prioritization Working Group procedure and removing I-prioritize.

@rustbot label -I-prioritize +P-medium

[Aaron1011]

@ZippyMagician: Can you share the original repository, or provide a self-contained reproduction of the issue?

[ZippyMagician]

@Aaron1011 here is one I got to error in the same way:

macro_rules! len {
    () => { 0 };
    ($item:literal) => { 1 };
    ($item:literal, $($extras:literal),*) => { 1 + len!($($extras),*); }
}

macro_rules! slice {
    ($($item:literal),*) => {
        const SIZED: [&str; len!($($item),*)] = [$($item),*];
    }
}

slice!["first", "second", "third", "last"];

fn main() {
    println!("{:?}", SIZED);
}

I also noticed this warning that I believe I failed to include in the original issue:

warning: Error finalizing incremental compilation session directory `~/Projects/rust/bug_report/target/debug/incremental/bug_report-33rm2tncuoqcs/s-fxpjcgkcte-lqvmgv-working`: No such file or directory (os error 2)

If I remove the semicolon, this warning does not show up, and the program works as expected.