ICE: "expected exactly one expression"

Code

fn main() {
    let _ = #[test] ();
}

Error output

error[E0658]: attributes on expressions are experimental
 --> ./src/test/compile-fail/cfg-non-opt-expr.rs:3:13
  |
3 |     let _ = #[test] ();
  |             ^^^^^^^
  |
  = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
  = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable

thread 'rustc' panicked at 'expected exactly one expression', compiler/rustc_expand/src/expand.rs:277:30
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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 1.50.0-nightly (1f5bc176b 2020-12-19) running on x86_64-unknown-linux-gnu

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

For more information about this error, try `rustc --explain E0658`.

Backtrace

error[E0658]: attributes on expressions are experimental
 --> ./src/test/compile-fail/cfg-non-opt-expr.rs:3:13
  |
3 |     let _ = #[test] ();
  |             ^^^^^^^
  |
  = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
  = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable

thread 'rustc' panicked at 'expected exactly one expression', compiler/rustc_expand/src/expand.rs:277:30
stack backtrace:
   0:     0x7f93b0be36c7 - std::backtrace_rs::backtrace::libunwind::trace::h746c3e9529d524bc
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/../../backtrace/src/backtrace/libunwind.rs:90:5
   1:     0x7f93b0be36c7 - std::backtrace_rs::backtrace::trace_unsynchronized::h84373278bfb39e0c
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f93b0be36c7 - std::sys_common::backtrace::_print_fmt::h517324efde750597
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7f93b0be36c7 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hf594ab77fac89284
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x7f93b0c5428c - core::fmt::write::h3868db8542c90941
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/core/src/fmt/mod.rs:1078:17
   5:     0x7f93b0bd5592 - std::io::Write::write_fmt::h3f6656f045fa877f
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/io/mod.rs:1519:15
   6:     0x7f93b0be73b5 - std::sys_common::backtrace::_print::hda7655c057c24dcc
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/sys_common/backtrace.rs:49:5
   7:     0x7f93b0be73b5 - std::sys_common::backtrace::print::h546a6c8431d46287
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/sys_common/backtrace.rs:36:9
   8:     0x7f93b0be73b5 - std::panicking::default_hook::{{closure}}::h006dd083853faf51
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/panicking.rs:208:50
   9:     0x7f93b0be6f0a - std::panicking::default_hook::hf0f9afb1017317fc
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/panicking.rs:225:9
  10:     0x7f93b1487ea8 - rustc_driver::report_ice::h956234bae73e460f
  11:     0x7f93b0be7cb6 - std::panicking::rust_panic_with_hook::hb7a19826c029b1d6
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/panicking.rs:595:17
  12:     0x7f93b0be77d7 - std::panicking::begin_panic_handler::{{closure}}::hde71edcd925d0c5e
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/panicking.rs:497:13
  13:     0x7f93b0be3b8c - std::sys_common::backtrace::__rust_end_short_backtrace::h8a3c7d6cea578919
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/sys_common/backtrace.rs:141:18
  14:     0x7f93b0be7739 - rust_begin_unwind
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/panicking.rs:493:5
  15:     0x7f93b0c506a1 - core::panicking::panic_fmt::h20225113c4a2f8fd
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/core/src/panicking.rs:92:14
  16:     0x7f93b0c50283 - core::option::expect_failed::h8be1ca96ca0d69ca
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/core/src/option.rs:1260:5
  17:     0x7f93b351fbd3 - rustc_expand::expand::AstFragmentKind::expect_from_annotatables::h05fc875ee2cd0717
  18:     0x7f93b3522cfd - rustc_expand::expand::MacroExpander::fully_expand_fragment::he26fff039b78329f
  19:     0x7f93b3520d8e - rustc_expand::expand::MacroExpander::expand_crate::hd5614e1080b391fe
  20:     0x7f93b16bf498 - rustc_session::utils::<impl rustc_session::session::Session>::time::h2ca8885ebbb2a4d1
  21:     0x7f93b16fe248 - rustc_interface::passes::configure_and_expand_inner::h90f77254651e066c
  22:     0x7f93b16b7697 - rustc_interface::passes::configure_and_expand::{{closure}}::h711307f1fc684295
  23:     0x7f93b16a87cf - rustc_data_structures::box_region::PinnedGenerator<I,A,R>::new::h2878e50656ccab01
  24:     0x7f93b16fd488 - rustc_interface::passes::configure_and_expand::ha44c525d7e0c6049
  25:     0x7f93b175a52f - rustc_interface::queries::Queries::expansion::h3a59c340f40b4f2f
  26:     0x7f93b14f5751 - rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter::h58cc75bad344bc3b
  27:     0x7f93b14b1597 - rustc_span::with_source_map::hb087a1c2bc75d8e9
  28:     0x7f93b14f6f8b - rustc_interface::interface::create_compiler_and_run::ha492945fb183c01e
  29:     0x7f93b14c5530 - scoped_tls::ScopedKey<T>::set::hf41307147817b997
  30:     0x7f93b14d67c7 - std::sys_common::backtrace::__rust_begin_short_backtrace::h645f3b510f7fe2fd
  31:     0x7f93b144b7ea - core::ops::function::FnOnce::call_once{{vtable.shim}}::h19b1a0a715ec4eae
  32:     0x7f93b0bf77ba - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hea1090dbdcecbf5a
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/alloc/src/boxed.rs:1328:9
  33:     0x7f93b0bf77ba - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h8d5723d3912bd325
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/alloc/src/boxed.rs:1328:9
  34:     0x7f93b0bf77ba - std::sys::unix::thread::Thread::new::thread_start::hc17a425ca2995724
                               at /rustc/1f5bc176b0e54a8e464704adcd7e571700207fe9/library/std/src/sys/unix/thread.rs:71:17
  35:     0x7f93b0ae83e9 - start_thread
  36:     0x7f93b0a05293 - __GI___clone
  37:                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 1.50.0-nightly (1f5bc176b 2020-12-19) running on x86_64-unknown-linux-gnu

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

For more information about this error, try `rustc --explain E0658`.

@rustbot

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

Had to uninstall ~20 gigs of rustc releases again but since this code does not ICE on 1.20 but ices on 1.48.0, this is a stable-to-stable ice.

This started ICE'ing in 1.30.0.

Error message in 1.29.0:

error[E0658]: attributes on expressions are experimental. (see issue #15701)
 --> <source>:2:13
  |
2 |     let _ = #[test] ();
  |             ^^^^^^^

error: removing an expression is not supported in this position
 --> <source>:2:13
  |
2 |     let _ = #[test] ();
  |             ^^^^^^^

error: aborting due to 2 previous errors

This is not supposed to work yet and it gives a good error message saying so -> P-low

Assigning P-low and removing I-prioritize as discussed in the prioritization working group.

The error message is helpful but it still panics in nightly. Do we want to fix the ICE at least or keep it?

A possible duplicate.

const CR: i32 = #[test]
C;

Fixed in #83814.

Rollup merge of rust-lang#83814 - petrochenkov:emptyexpr, r=davidtwco

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ICE: "expected exactly one expression" #80251

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ICE: "expected exactly one expression" #80251

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matthiaskrgr commented on Dec 21, 2020

LeSeulArtichaut commented on Dec 21, 2020

camelid commented on Dec 21, 2020

osa1 commented on Jan 27, 2021

chengniansun commented on Mar 25, 2021

petrochenkov commented on Apr 3, 2021

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