ICE: 'internal error: entered unreachable code', compiler/rustc_parse/src/parser/item.rs:1723:17

[Cancelll]

Code

trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ self , ... , ... , ... , ... , ... , ... , ... , ... , ... , ) -> && '_ mut ( ) ;
}

Meta

rustc --version --verbose:

rustc 1.54.0-nightly (35fff69d0 2021-06-06)
binary: rustc
commit-hash: 35fff69d043b1c0f5c29894e7f4b0da8b039c131
commit-date: 2021-06-06
host: x86_64-unknown-linux-gnu
release: 1.54.0-nightly
LLVM version: 12.0.1

Error output

error: character literal may only contain one codepoint
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:75
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ s...
  |                                                                          ^^^^^^^^^
  |
help: if you meant to write a `str` literal, use double quotes
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' "default" 'async' '&raw' ] & '?ဪൈ self , ... , ... , ... , ... , ... , ... , ... , ... , ... , ) -> && '_ mut ( ) ;
  |                                                                          ^^^^^^^^^

error: character literal may only contain one codepoint
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:85
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ s...
  |                                                                                    ^^^^^^^
  |
help: if you meant to write a `str` literal, use double quotes
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' "async" '&raw' ] & '?ဪൈ self , ... , ... , ... , ... , ... , ... , ... , ... , ... , ) -> && '_ mut ( ) ;
  |                                                                                    ^^^^^^^

error: character literal may only contain one codepoint
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:93
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ s...
  |                                                                                            ^^^^^^
  |
help: if you meant to write a `str` literal, use double quotes
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' "&raw" ] & '?ဪൈ self , ... , ... , ... , ... , ... , ... , ... , ... , ... , ) -> && '_ mut ( ) ;
  |                                                                                            ^^^^^^

error: character literal may only contain one codepoint
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:104
  |
1 | ...ync' '&raw' ] & '?ဪൈ self , ... , ... , ... , ... , ... , ... , ... , ... , ... , ) -> && '_ mut ( ...
  |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
help: if you meant to write a `str` literal, use double quotes
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & "?ဪൈ self , ... , ... , ... , ... , ... , ... , ... , ... , ... , ) -> && "_ mut ( ) ;
  |                                                                                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: underscore literal suffix is not allowed
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:180
  |
1 | ... , ... , ... , ... , ... , ... , ... , ... , ) -> && '_ mut ( ) ;
  |                                                         ^
  |
  = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
  = note: see issue #42326 <https://github.com/rust-lang/rust/issues/42326> for more information

error[E0670]: `async fn` is not permitted in Rust 2015
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:20
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ s...
  |                    ^^^^^ to use `async fn`, switch to Rust 2018 or later
  |
  = help: set `edition = "2018"` in `Cargo.toml`
  = note: for more on editions, read https://doc.rust-lang.org/edition-guide

error: expected identifier, found `']'`
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:67
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ s...
  |                                                                  ^^^ expected identifier

error: expected one of `)`, `,`, `->`, `;`, `where`, or `{`, found `]`
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:100
  |
1 | ...�áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ self , ... , ... , ... , ... , ... ,...
  |                         -                                     -^
  |                         |                                     |
  |                         unclosed delimiter                    help: `)` may belong here

thread 'rustc' panicked at 'internal error: entered unreachable code', compiler/rustc_parse/src/parser/item.rs:1723:17
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 1.54.0-nightly (35fff69d0 2021-06-06) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z mir-opt-level=3 -Z new-llvm-pass-manager=yes -Z unsound-mir-opts=yes -Z polonius=yes -Z polymorphize=yes -C debuginfo=2 -C opt-level=3 --crate-type staticlib

query stack during panic:
end of query stack
error: aborting due to 7 previous errors; 1 warning emitted

For more information about this error, try `rustc --explain E0670`.

Backtrace

error: character literal may only contain one codepoint
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:75
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ s...
  |                                                                          ^^^^^^^^^
  |
help: if you meant to write a `str` literal, use double quotes
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' "default" 'async' '&raw' ] & '?ဪൈ self , ... , ... , ... , ... , ... , ... , ... , ... , ... , ) -> && '_ mut ( ) ;
  |                                                                          ^^^^^^^^^

error: character literal may only contain one codepoint
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:85
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ s...
  |                                                                                    ^^^^^^^
  |
help: if you meant to write a `str` literal, use double quotes
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' "async" '&raw' ] & '?ဪൈ self , ... , ... , ... , ... , ... , ... , ... , ... , ... , ) -> && '_ mut ( ) ;
  |                                                                                    ^^^^^^^

error: character literal may only contain one codepoint
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:93
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ s...
  |                                                                                            ^^^^^^
  |
help: if you meant to write a `str` literal, use double quotes
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' "&raw" ] & '?ဪൈ self , ... , ... , ... , ... , ... , ... , ... , ... , ... , ) -> && '_ mut ( ) ;
  |                                                                                            ^^^^^^

error: character literal may only contain one codepoint
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:104
  |
1 | ...ync' '&raw' ] & '?ဪൈ self , ... , ... , ... , ... , ... , ... , ... , ... , ... , ) -> && '_ mut ( ...
  |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
help: if you meant to write a `str` literal, use double quotes
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & "?ဪൈ self , ... , ... , ... , ... , ... , ... , ... , ... , ... , ) -> && "_ mut ( ) ;
  |                                                                                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: underscore literal suffix is not allowed
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:180
  |
1 | ... , ... , ... , ... , ... , ... , ... , ... , ) -> && '_ mut ( ) ;
  |                                                         ^
  |
  = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
  = note: see issue #42326 <https://github.com/rust-lang/rust/issues/42326> for more information

error[E0670]: `async fn` is not permitted in Rust 2015
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:20
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ s...
  |                    ^^^^^ to use `async fn`, switch to Rust 2018 or later
  |
  = help: set `edition = "2018"` in `Cargo.toml`
  = note: for more on editions, read https://doc.rust-lang.org/edition-guide

error: expected identifier, found `']'`
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:67
  |
1 | trait Tr : Sized { async extern r###"��áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ s...
  |                                                                  ^^^ expected identifier

error: expected one of `)`, `,`, `->`, `;`, `where`, or `{`, found `]`
 --> default_finding_folder_rust/crash_20210605_014058_0055/delta/perses_result/mutant.rs:1:100
  |
1 | ...�áÖ@"### fn union < > ( # [ ']' '[' 'default' 'async' '&raw' ] & '?ဪൈ self , ... , ... , ... , ... , ... ,...
  |                         -                                     -^
  |                         |                                     |
  |                         unclosed delimiter                    help: `)` may belong here

thread 'rustc' panicked at 'internal error: entered unreachable code', compiler/rustc_parse/src/parser/item.rs:1723:17
stack backtrace:
   0: rust_begin_unwind
             at /rustc/35fff69d043b1c0f5c29894e7f4b0da8b039c131/library/std/src/panicking.rs:515:5
   1: core::panicking::panic_fmt
             at /rustc/35fff69d043b1c0f5c29894e7f4b0da8b039c131/library/core/src/panicking.rs:92:14
   2: core::panicking::panic
             at /rustc/35fff69d043b1c0f5c29894e7f4b0da8b039c131/library/core/src/panicking.rs:50:5
   3: rustc_parse::parser::item::<impl rustc_parse::parser::Parser>::parse_fn
   4: rustc_parse::parser::item::<impl rustc_parse::parser::Parser>::parse_item_kind
   5: rustc_parse::parser::item::<impl rustc_parse::parser::Parser>::parse_item_common
   6: rustc_parse::parser::item::<impl rustc_parse::parser::Parser>::parse_assoc_item
   7: rustc_parse::parser::item::<impl rustc_parse::parser::Parser>::parse_item_kind
   8: rustc_parse::parser::item::<impl rustc_parse::parser::Parser>::parse_item_common
   9: rustc_parse::parser::item::<impl rustc_parse::parser::Parser>::parse_mod
  10: rustc_parse::parse_crate_from_file
  11: rustc_interface::passes::parse
  12: rustc_interface::queries::Queries::parse
  13: rustc_span::with_session_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose 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 1.54.0-nightly (35fff69d0 2021-06-06) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z mir-opt-level=3 -Z new-llvm-pass-manager=yes -Z unsound-mir-opts=yes -Z polonius=yes -Z polymorphize=yes -C debuginfo=2 -C opt-level=3 --crate-type staticlib

query stack during panic:
end of query stack
error: aborting due to 7 previous errors; 1 warning emitted

For more information about this error, try `rustc --explain E0670`.

[Cancelll]

Possibly related to #81804

[leonardo-m]

Was this bug found by fuzzing?

[Cancelll]

Was this bug found by fuzzing?

yes

[hellow554]

trait Tr {
    fn union(#[]
}

fn main() {}

I can confirm that this issue referes to the same rollup as #81804 (which was suggested by cancelll as a possible duplicate). Therefore I would suggest adding this to the other issue as an example that will be added as a testcase and close this :)

On a second thought, the only difference is that this is a trait function instead of a plain function, therefore a possible fix should cover both...

[JohnTitor]

Closing as duplicate, added this case to #81804 (comment) just in case.