"the compiler hit an unexpected failure path": implementing Drop on struct with closure field

[DanielKeep]

Failure with rustc 0.11.0-pre-nightly (5d5c20647f45f2eb74f337e5434bbe63b0c43345 2014-07-03 21:46:47 +0000), running on 64-bit Windows 7 SP1.

Source file src\bug.rs:

fn main() {
}

struct OnExitSentinel<'a> {
    block: ||: 'a,
}

impl<'a> Drop for OnExitSentinel<'a> {
    fn drop(&mut self) {
    }
}

Compiled with: rustc src\bug.rs, produces the following:

error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
task 'rustc' failed at 'index out of bounds: the len is 0 but the index is 0', C:\bot\slave\nightly-win\build\src\librustc\lib.rs:1

stack backtrace:
   1: 0x70dc22de
   2: 0x701c9401
   3: 0x701c8f63
   4: 0x701c8d9e
   5: 0x70212848
   6: 0x7021501f
   7: 0x65344bd4
   8: 0x652e560f
   9: 0x652e5150
  10: 0x654661f9
  11: 0x653290b4
  12: 0x654921f9
  13: 0x6542be89
  14: 0x657c3a42
  15: 0x657c5b3a
  16: 0x65b39984
  17: 0x65abda79
  18: 0x65ab81b3
  19: 0x65b5a95c
  20: 0x65b5834d
  21: 0x65b6af0e
  22: 0x65b6ae00
  23: 0x6416fe53
  24: 0x701c8bb5
  25: 0x701c5e03
  26: 0x6416fcfc
  27: 0x701c870f
  28: 0x77849f72

The stack trace is, I admit, not terribly useful. I don't know how to get more information out of it.

If you require any further information, let me know. Happy to help.

[alexcrichton]

Closing as a dupe of #14889, and moving the test case over to there as well.