Internal Compiler Error @ parser.rs:446:22

[JulianKnodt]

When compiling a personal project, I got an error that the compiler panicked and entered unreachable code.

I've dumped the output:

    Checking small_sat v0.1.0 (/Users/julianknodt/Desktop/programming/projects/rustjects/small_sat)
error: incorrect close delimiter: `}`
  --> src/watch_list.rs:88:9
   |
85 |         match next {
   |                    - close delimiter possibly meant for this
86 |           None => self.units.push(,
   |                                  - un-closed delimiter
87 |           Some(next) => todo.push((other_lit, cref, next)),
88 |         }
   |         ^ incorrect close delimiter

error: incorrect close delimiter: `}`
  --> src/watch_list.rs:95:5
   |
91 |     for (watched_lit, clause, next) in todo {
   |                                             - close delimiter possibly meant for this
92 |       self.occurrences[watched_lit.raw()].iter_mut().find(|
   |                                                          - un-closed delimiter
...
95 |     }
   |     ^ incorrect close delimiter

error: expected one of `:`, `;`, `=`, `@`, or `|`, found `if`
  --> src/watch_list.rs:77:5
   |
75 |     let new_units
   |                  - help: a semicolon may be missing here
76 | 
77 |     if let Some(clauses) = self.occurrences.get_mut(lit.raw() as usize) {
   |     ^^

error: expected expression, found `,`
  --> src/watch_list.rs:86:35
   |
86 |           None => self.units.push(,
   |                --                 ^ expected expression
   |                |
   |                while parsing the `match` arm starting here

error: expected one of `,`, `::`, or `:`, found `.`
  --> src/watch_list.rs:93:13
   |
93 |         self.occurrences[watched_lit.raw() as usize].insert(clause, *next),
   |             ^ expected one of `,`, `::`, or `:` here

error: expected one of `,`, `:`, or `@`, found `[`
  --> src/watch_list.rs:93:25
   |
93 |         self.occurrences[watched_lit.raw() as usize].insert(clause, *next),
   |                         ^ expected one of `,`, `:`, or `@` here

error: expected one of `,`, `@`, `]`, or `|`, found `.`
  --> src/watch_list.rs:93:37
   |
93 |         self.occurrences[watched_lit.raw() as usize].insert(clause, *next),
   |                                     ^ expected one of `,`, `@`, `]`, or `|` here

error: expected one of `,`, `]`, or `|`, found `as`
  --> src/watch_list.rs:93:44
   |
93 |         self.occurrences[watched_lit.raw() as usize].insert(clause, *next),
   |                                            ^^ expected one of `,`, `]`, or `|` here

error: expected identifier, found keyword `as`
  --> src/watch_list.rs:93:44
   |
93 |         self.occurrences[watched_lit.raw() as usize].insert(clause, *next),
   |                                            ^^ expected identifier, found keyword
   |
help: you can escape reserved keywords to use them as identifiers
   |
93 |         self.occurrences[watched_lit.raw() r#as usize].insert(clause, *next),
   |                                            ^^^^

error: expected one of `,`, `@`, `]`, or `|`, found `usize`
  --> src/watch_list.rs:93:47
   |
93 |         self.occurrences[watched_lit.raw() as usize].insert(clause, *next),
   |                                               ^^^^^ expected one of `,`, `@`, `]`, or `|` here

error: expected one of `,` or `:`, found `.`
  --> src/watch_list.rs:93:53
   |
93 |         self.occurrences[watched_lit.raw() as usize].insert(clause, *next),
   |                                                     ^ expected one of `,` or `:` here

error: expected one of `)`, `-`, `_`, `box`, `mut`, `ref`, `|`, identifier, or path, found `*`
  --> src/watch_list.rs:93:69
   |
86 |           None => self.units.push(,
   |                                  - unclosed delimiter
...
93 |         self.occurrences[watched_lit.raw() as usize].insert(clause, *next),
   |                                                                    -^
   |                                                                    |
   |                                                                    help: `)` may belong here

thread 'rustc' panicked at 'internal error: entered unreachable code', src/libsyntax/parse/parser.rs:446:22
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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.40.0-nightly (95f437b3c 2019-10-27) running on x86_64-apple-darwin

note: compiler flags: -C debuginfo=2 -C incremental --crate-type lib

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

error: aborting due to 12 previous errors

error: could not compile `small_sat`.

To learn more, run the command again with --verbose.

And I committed my code which caused the bug here:
JulianKnodt/small_sat@5e82572

It might be because I had only written half of an anonymous function at watch_list.rs at line 92.

This is not that urgent as I only saw it with half-written code, but since the compiler suggested I file a bug I did.

rustc --version --verbose:

rustc 1.40.0-nightly (95f437b3c 2019-10-27)
binary: rustc
commit-hash: 95f437b3cfb2fec966d7eaf69d7c2e36f9c274d1
commit-date: 2019-10-27
host: x86_64-apple-darwin
release: 1.40.0-nightly
LLVM version: 9.0

[memoryruins]

It might be because I had only written half of an anonymous function at watch_list.rs at line 92.

Good call! Reducing it to fn f() { |[](* } is enough to trigger the ICE.

backtrace

thread 'rustc' panicked at 'internal error: entered unreachable code', src/librustc_parse/parser/mod.rs:446:22
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:77
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:61
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1030
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1412
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:65
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:50
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:188
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:205
  10: rustc_driver::report_ice
  11: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:468
  12: std::panicking::begin_panic
  13: rustc_parse::parser::expr::<impl rustc_parse::parser::Parser>::parse_closure_expr
  14: rustc_parse::parser::expr::<impl rustc_parse::parser::Parser>::parse_bottom_expr
  15: rustc_parse::parser::expr::<impl rustc_parse::parser::Parser>::parse_dot_or_call_expr
  16: rustc_parse::parser::expr::<impl rustc_parse::parser::Parser>::parse_prefix_expr
  17: rustc_parse::parser::expr::<impl rustc_parse::parser::Parser>::parse_assoc_expr_with
  18: rustc_parse::parser::stmt::<impl rustc_parse::parser::Parser>::parse_stmt_without_recovery
  19: rustc_parse::parser::stmt::<impl rustc_parse::parser::Parser>::parse_full_stmt
  20: rustc_parse::parser::stmt::<impl rustc_parse::parser::Parser>::parse_block_tail
  21: rustc_parse::parser::stmt::<impl rustc_parse::parser::Parser>::parse_inner_attrs_and_block
  22: rustc_parse::parser::item::<impl rustc_parse::parser::Parser>::parse_item_fn
  23: rustc_parse::parser::item::<impl rustc_parse::parser::Parser>::parse_item_implementation
  24: rustc_parse::parser::item::<impl rustc_parse::parser::Parser>::parse_item_
  25: rustc_parse::parser::item::<impl rustc_parse::parser::Parser>::parse_item
  26: rustc_parse::parser::module::<impl rustc_parse::parser::Parser>::parse_mod_items
  27: rustc_parse::parser::module::<impl rustc_parse::parser::Parser>::parse_crate_mod
  28: rustc_parse::parse_crate_from_file
  29: rustc_interface::passes::parse::{{closure}}
  30: rustc_interface::passes::parse
  31: rustc_interface::queries::Query<T>::compute
  32: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::parse
  33: rustc_interface::interface::run_compiler_in_existing_thread_pool
  34: std::thread::local::LocalKey<T>::with
  35: scoped_tls::ScopedKey<T>::set
  36: syntax::with_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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.40.0-nightly (4f03f4a98 2019-11-12) running on x86_64-unknown-linux-gnu

note: compiler flags: -C codegen-units=1 -C debuginfo=2 --crate-type lib

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

query stack during panic:
end of query stack
error: aborting due to 2 previous errors

https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=8486aeccb8fba32337178ccb6937bce0

[hellow554]

@rustbot modify labels: I-ICE T-compiler C-bug A-frontend

[Centril]

I've traced the problem down to this call:

rust/src/librustc_parse/parser/expr.rs

Line 1344 in 374ad1b

self.expect_or()?;

[pnkfelix]

triage: P-high, removing nomination label.