Parser crashes after encountering invalid variable declaration in macro call

[fmease]

Code

macro_rules! m { ($s:stmt) => {} }
m! { var x }

Meta

rustc --Vv:

rustc 1.66.0-nightly (9062b780b 2022-09-21)
binary: rustc
commit-hash: 9062b780b32d2eab060b4432863e085d9504ca5c
commit-date: 2022-09-21
host: x86_64-unknown-linux-gnu
release: 1.66.0-nightly
LLVM version: 15.0.0

Error output

error: invalid variable declaration
 --> t.rs:2:6
  |
2 | m! { var x }
  |      ^^^
  |
help: write `let` instead of `var` to introduce a new variable
  |
2 | m! { let x }
  |      ~~~

Backtrace

thread 'rustc' panicked at 'Missing tokens for nt NtStmt(..) at t.rs:2:6: 2:11 (#0): "let x;"', /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/compiler/rustc_parse/src/parser/nonterminal.rs:187:13
stack backtrace:
   0:     0x7f963a96e010 - std::backtrace_rs::backtrace::libunwind::trace::hb70cd2c4f10319c4
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   1:     0x7f963a96e010 - std::backtrace_rs::backtrace::trace_unsynchronized::h6a235690bde8066a
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f963a96e010 - std::sys_common::backtrace::_print_fmt::hf423a9f93de17924
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7f963a96e010 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h81fafbb534b53ab7
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7f963a9c8e5e - core::fmt::write::h91215ed98af09b40
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/core/src/fmt/mod.rs:1202:17
   5:     0x7f963a95eb15 - std::io::Write::write_fmt::h9d32a42fc3233c10
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/io/mod.rs:1679:15
   6:     0x7f963a970d93 - std::sys_common::backtrace::_print::hebe110643c78e1a1
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7f963a970d93 - std::sys_common::backtrace::print::h544b1b31fddff6eb
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7f963a970d93 - std::panicking::default_hook::{{closure}}::hf97dcba6b32ea332
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/panicking.rs:267:22
   9:     0x7f963a970a7f - std::panicking::default_hook::h3f82dc02801e0576
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/panicking.rs:286:9
  10:     0x7f963d1748d1 - <rustc_driver[610c3dabcb482a3]::DEFAULT_HOOK::{closure#0}::{closure#0} as core[c7389bc70673082e]::ops::function::FnOnce<(&core[c7389bc70673082e]::panic::panic_info::PanicInfo,)>>::call_once::{shim:vtable#0}
  11:     0x7f963a9715cb - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h1442642a89018d6d
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/alloc/src/boxed.rs:1954:9
  12:     0x7f963a9715cb - std::panicking::rust_panic_with_hook::hb8c8dca0bdad40db
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/panicking.rs:673:13
  13:     0x7f963a971427 - std::panicking::begin_panic_handler::{{closure}}::hd6686af6943caeb9
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/panicking.rs:560:13
  14:     0x7f963a96e4bc - std::sys_common::backtrace::__rust_end_short_backtrace::h83dd31235af00771
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/sys_common/backtrace.rs:138:18
  15:     0x7f963a971142 - rust_begin_unwind
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/panicking.rs:556:5
  16:     0x7f963a9c5a33 - core::panicking::panic_fmt::h261ed3d4efd89943
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/core/src/panicking.rs:142:14
  17:     0x7f963be7c627 - <rustc_expand[f42067b102e05961]::mbe::macro_parser::TtParser>::parse_tt
  18:     0x7f963be76c43 - <rustc_expand[f42067b102e05961]::mbe::macro_rules::MacroRulesMacroExpander as rustc_expand[f42067b102e05961]::base::TTMacroExpander>::expand
  19:     0x7f963c872ed2 - <rustc_expand[f42067b102e05961]::expand::MacroExpander>::fully_expand_fragment
  20:     0x7f963bf4cc13 - <rustc_expand[f42067b102e05961]::expand::MacroExpander>::expand_crate
  21:     0x7f963bf4be24 - <rustc_session[40303a05d79b8f9]::session::Session>::time::<core[c7389bc70673082e]::result::Result<rustc_ast[8659774c93938f42]::ast::Crate, rustc_errors[275d4fb119ffacfb]::ErrorGuaranteed>, rustc_interface[121647ee48321f2a]::passes::configure_and_expand::{closure#1}>
  22:     0x7f963bf14083 - rustc_interface[121647ee48321f2a]::passes::configure_and_expand
  23:     0x7f963bf0ac85 - <rustc_interface[121647ee48321f2a]::queries::Queries>::expansion
  24:     0x7f963bf0764c - rustc_interface[121647ee48321f2a]::interface::create_compiler_and_run::<core[c7389bc70673082e]::result::Result<(), rustc_errors[275d4fb119ffacfb]::ErrorGuaranteed>, rustc_driver[610c3dabcb482a3]::run_compiler::{closure#1}>
  25:     0x7f963bf06072 - <scoped_tls[d2720ff23ff3c466]::ScopedKey<rustc_span[d840d66cf15b0e9]::SessionGlobals>>::set::<rustc_interface[121647ee48321f2a]::interface::run_compiler<core[c7389bc70673082e]::result::Result<(), rustc_errors[275d4fb119ffacfb]::ErrorGuaranteed>, rustc_driver[610c3dabcb482a3]::run_compiler::{closure#1}>::{closure#0}, core[c7389bc70673082e]::result::Result<(), rustc_errors[275d4fb119ffacfb]::ErrorGuaranteed>>
  26:     0x7f963bf05d5f - std[2c19137f19a9cec7]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[121647ee48321f2a]::util::run_in_thread_pool_with_globals<rustc_interface[121647ee48321f2a]::interface::run_compiler<core[c7389bc70673082e]::result::Result<(), rustc_errors[275d4fb119ffacfb]::ErrorGuaranteed>, rustc_driver[610c3dabcb482a3]::run_compiler::{closure#1}>::{closure#0}, core[c7389bc70673082e]::result::Result<(), rustc_errors[275d4fb119ffacfb]::ErrorGuaranteed>>::{closure#0}, core[c7389bc70673082e]::result::Result<(), rustc_errors[275d4fb119ffacfb]::ErrorGuaranteed>>
  27:     0x7f963cfda9d0 - <<std[2c19137f19a9cec7]::thread::Builder>::spawn_unchecked_<rustc_interface[121647ee48321f2a]::util::run_in_thread_pool_with_globals<rustc_interface[121647ee48321f2a]::interface::run_compiler<core[c7389bc70673082e]::result::Result<(), rustc_errors[275d4fb119ffacfb]::ErrorGuaranteed>, rustc_driver[610c3dabcb482a3]::run_compiler::{closure#1}>::{closure#0}, core[c7389bc70673082e]::result::Result<(), rustc_errors[275d4fb119ffacfb]::ErrorGuaranteed>>::{closure#0}, core[c7389bc70673082e]::result::Result<(), rustc_errors[275d4fb119ffacfb]::ErrorGuaranteed>>::{closure#1} as core[c7389bc70673082e]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  28:     0x7f963a97b3b3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::he225f53d02ef001f
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/alloc/src/boxed.rs:1940:9
  29:     0x7f963a97b3b3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h1d16365b1f15b7b7
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/alloc/src/boxed.rs:1940:9
  30:     0x7f963a97b3b3 - std::sys::unix::thread::Thread::new::thread_start::h91bd867cccfe281f
                               at /rustc/9062b780b32d2eab060b4432863e085d9504ca5c/library/std/src/sys/unix/thread.rs:108:17
  31:     0x7f963a71f78d - <unknown>
  32:     0x7f963a7a08e4 - clone
  33:                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 1.66.0-nightly (9062b780b 2022-09-21) running on x86_64-unknown-linux-gnu

query stack during panic:
end of query stack
error: aborting due to previous error

@rustbot label A-parser A-macros

[chenyukang]

@rustbot claim

[compiler-errors]

cc @Nilstrieb this should probably be gated with your "may eagerly recover" work as well

[fmease]

This code is actually already mentioned in #103534 ;)

[ohno418]

@rustbot claim

[Noratrieb]

Yeah, gating this recovery behind a self.may_recover() is the correct fix here.

[Noratrieb]

Also very fun that these things can ICE sometimes.

[ohno418]

Found these also panic:

m! { mut x }
m! { auto x }

Since these are highly related to the var case, one pull request can fix all of these (maybe).