nightly ICE: panicked at 'index out of bounds: the len is 0 but the index is 1', /checkout/src/liballoc/vec.rs:1564:14

[zhendongsu]

The test also causes 1.18 and 1.19 to loop indefinitely.

$ rustc-nightly --version
rustc 1.21.0-nightly (8c303ed87 2017-08-20)
$ 
$ rustc-nightly tmp.rs
error: expected expression, found `}`
 --> tmp.rs:4:1
  |
4 | } 
  | ^

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 1.21.0-nightly (8c303ed87 2017-08-20) running on i686-unknown-linux-gnu

thread 'rustc' panicked at 'index out of bounds: the len is 0 but the index is 1', /checkout/src/liballoc/vec.rs:1564:14
note: Run with `RUST_BACKTRACE=1` for a backtrace.

$ 
$ cat tmp.rs
impl Struct
{ 
  fn static_meth_struct () -> Struct {|} 
} 
$ 

[zhendongsu]

$ RUST_BACKTRACE=1 rustc-nightly tmp.rs
error: expected expression, found `}`
 --> tmp.rs:4:1
  |
4 | }
  | ^

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 1.21.0-nightly (8c303ed87 2017-08-20) running on i686-unknown-linux-gnu

note: run with `RUST_BACKTRACE=1` for a backtrace

thread 'rustc' panicked at 'index out of bounds: the len is 0 but the index is 1', /checkout/src/liballoc/vec.rs:1564:14
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /checkout/src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/sys_common/backtrace.rs:60
             at /checkout/src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:391
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:611
   5: std::panicking::begin_panic
             at /checkout/src/libstd/panicking.rs:572
   6: std::panicking::begin_panic_fmt
             at /checkout/src/libstd/panicking.rs:522
   7: rust_begin_unwind
             at /checkout/src/libstd/panicking.rs:498
   8: core::panicking::panic_fmt
             at /checkout/src/libcore/panicking.rs:71
   9: core::panicking::panic_bounds_check
             at /checkout/src/libcore/panicking.rs:58
  10: syntax::parse::parser::Parser::parse_impl_item
  11: syntax::parse::parser::Parser::parse_item_impl
  12: syntax::parse::parser::Parser::parse_item_
  13: syntax::parse::parser::Parser::parse_item
  14: syntax::parse::parser::Parser::parse_mod_items
  15: syntax::parse::parser::Parser::parse_crate_mod
  16: syntax::parse::parse_crate_from_file
  17: rustc_driver::driver::phase_1_parse_input::{{closure}}
  18: rustc_driver::driver::phase_1_parse_input
  19: rustc_driver::driver::compile_input
  20: rustc_driver::run_compiler

$

[arielb1]

With more line numbers:

thread 'rustc' panicked at 'index out of bounds: the len is 0 but the index is 1', /home/ariel/Rust/rust/src/liballoc/vec.rs:1564:14
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /home/ariel/Rust/rust/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /home/ariel/Rust/rust/src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at /home/ariel/Rust/rust/src/libstd/sys_common/backtrace.rs:60
             at /home/ariel/Rust/rust/src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at /home/ariel/Rust/rust/src/libstd/panicking.rs:391
   4: std::panicking::rust_panic_with_hook
             at /home/ariel/Rust/rust/src/libstd/panicking.rs:611
   5: std::panicking::begin_panic
             at /home/ariel/Rust/rust/src/libstd/panicking.rs:572
   6: std::panicking::begin_panic_fmt
             at /home/ariel/Rust/rust/src/libstd/panicking.rs:522
   7: rust_begin_unwind
             at /home/ariel/Rust/rust/src/libstd/panicking.rs:498
   8: core::panicking::panic_fmt
             at /home/ariel/Rust/rust/src/libcore/panicking.rs:71
   9: core::panicking::panic_bounds_check
             at /home/ariel/Rust/rust/src/libcore/panicking.rs:58
  10: syntax::parse::parser::Parser::parse_impl_item
             at /home/ariel/Rust/rust/src/liballoc/vec.rs:1564
             at /home/ariel/Rust/rust/src/libsyntax/parse/parser.rs:6102
             at /home/ariel/Rust/rust/src/libsyntax/parse/parser.rs:4760
  11: syntax::parse::parser::Parser::parse_item_impl
             at /home/ariel/Rust/rust/src/libsyntax/parse/parser.rs:5016
  12: syntax::parse::parser::Parser::parse_item_
             at /home/ariel/Rust/rust/src/libsyntax/parse/parser.rs:5954
  13: syntax::parse::parser::Parser::parse_item
             at /home/ariel/Rust/rust/src/libsyntax/parse/parser.rs:6125
             at /home/ariel/Rust/rust/src/libsyntax/parse/parser.rs:6098
             at /home/ariel/Rust/rust/src/libsyntax/parse/parser.rs:6124
  14: syntax::parse::parser::Parser::parse_mod_items
             at /home/ariel/Rust/rust/src/libsyntax/parse/parser.rs:5267
  15: syntax::parse::parser::Parser::parse_crate_mod
             at /home/ariel/Rust/rust/src/libsyntax/parse/parser.rs:6236
  16: syntax::parse::parse_crate_from_file
             at /home/ariel/Rust/rust/src/libsyntax/parse/mod.rs:101
  17: rustc_driver::driver::phase_1_parse_input::{{closure}}
             at /home/ariel/Rust/rust/src/librustc_driver/driver.rs:543
  18: rustc_driver::driver::phase_1_parse_input
             at /home/ariel/Rust/rust/src/librustc/util/common.rs:48
             at /home/ariel/Rust/rust/src/librustc_driver/driver.rs:540
  19: rustc_driver::driver::compile_input
             at /home/ariel/Rust/rust/src/librustc_driver/driver.rs:112
  20: rustc_driver::run_compiler
             at /home/ariel/Rust/rust/src/librustc_driver/lib.rs:316

[tirr-c]

After investigating the parser, I found out it panicked after trying to parse closure argument list.

impl Struct
{
  fn static_meth_struct () -> Struct {|x, y} // incomplete argument list
}

error: expected expression, found `}`
 --> src/lib.rs:7:1
  |
7 | }
  | ^

error: internal compiler error: unexpected panic

On stable(1.20.0), the compiler falls into the infinite loop.

---

parse_fn_block_decl incorrectly consumes (or, discards) } if matching | does not exist, because it assumes that | follows directly after the argument list.

[tirr-c]

I'm trying to fix this. expect instead of bump might help?