➜  lsystem git:(master) ✗ RUST_BACKTRACE=1 cargo run --verbose
   Compiling lsystem v0.0.1 (file:///home/martin/devel/rust/lsystem)
     Running `rustc /home/martin/devel/rust/lsystem/src/main.rs --crate-name main --crate-type bin -g --out-dir /home/martin/devel/rust/lsystem/target --dep-info /home/martin/devel/rust/lsystem/target/.fingerprint/lsystem-7b595b16559fa8a0/dep-bin-main -L /home/martin/devel/rust/lsystem/target -L /home/martin/devel/rust/lsystem/target/deps`
/home/martin/devel/rust/lsystem/src/main.rs:97:2: 97:13 warning: variant is never used: `Rotate`, #[warn(dead_code)] on by default
/home/martin/devel/rust/lsystem/src/main.rs:97 	Rotate(f64),
                                               	^~~~~~~~~~~
/home/martin/devel/rust/lsystem/src/main.rs:193:5: 193:29 warning: unused result which must be used, #[warn(unused_must_use)] on by default
/home/martin/devel/rust/lsystem/src/main.rs:193     f.write(svg.as_bytes());
                                                    ^~~~~~~~~~~~~~~~~~~~~~~~
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. 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' panicked at 'assertion failed: `(left == right) && (right == left)` (left: `1`, right: `0`)', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/librustc/middle/trans/callee.rs:527

stack backtrace:
   1:     0x7f50c11e1af0 - rt::backtrace::imp::write::h78410bf389422bb4Afq
   2:     0x7f50c11e4bf0 - failure::on_fail::h3d7a049ab1da182dXAq
   3:     0x7f50c5701e30 - unwind::begin_unwind_inner::ha5ca26286b78bd8fdSd
   4:     0x7f50c5701950 - unwind::begin_unwind_fmt::h9ff359c82ebbcec0FPd
   5:     0x7f50c60ee000 - middle::trans::callee::trans_fn_ref_with_substs::hba3cc0fc3ae63c2fsH3
   6:     0x7f50c60ec490 - middle::trans::callee::trans_fn_ref::hbed04a37ddcc3d41iv3
   7:     0x7f50c60f3b90 - middle::trans::callee::trans_call::closure.122815
   8:     0x7f50c60cfee0 - middle::trans::callee::trans_call_inner::h765bc0f373132f55c33
   9:     0x7f50c60f38f0 - middle::trans::callee::trans_call::h22a97bb74555f6a9wX3
  10:     0x7f50c61027d0 - middle::trans::expr::trans_rvalue_dps_unadjusted::h2e79515870b8d9b7vb6
  11:     0x7f50c61013c0 - middle::trans::expr::trans_unadjusted::h9c5dc3fa8657c5dc4x5
  12:     0x7f50c60c96e0 - middle::trans::expr::trans::ha0fb3a3e696abbeb0Q4
  13:     0x7f50c61051d0 - middle::trans::expr::trans_rvalue_stmt_unadjusted::hb05812fdbf8aff70C55
  14:     0x7f50c60c8100 - middle::trans::expr::trans_into::h7de437ceccd3170f6M4
  15:     0x7f50c60c7560 - middle::trans::controlflow::trans_stmt_semi::hb17250e6bfcc5df1T20
  16:     0x7f50c60c6b10 - middle::trans::controlflow::trans_stmt::h1be522340f9d5765GY0
  17:     0x7f50c60c8520 - middle::trans::controlflow::trans_block::h2312adc5fa1d51a7M30
  18:     0x7f50c6169320 - middle::trans::base::trans_closure::h9d901ce06cad238eZah
  19:     0x7f50c60bb680 - middle::trans::base::trans_fn::ha09553a9c93fac1dpmh
  20:     0x7f50c616c8e0 - middle::trans::meth::trans_impl::hd15dfa9665237035vvm
  21:     0x7f50c60b8dc0 - middle::trans::base::trans_item::h1df6a3542f77a529LFh
  22:     0x7f50c6173ac0 - middle::trans::base::trans_crate::hff425ad7a84b1aa0RDi
  23:     0x7f50c65ad990 - driver::driver::phase_4_translate_to_llvm::hafcc49239634692fcXA
  24:     0x7f50c65a4200 - driver::driver::compile_input::hb25c14dfa369b7d96tA
  25:     0x7f50c66268b0 - driver::run_compiler::h3e5318d61e864690KgE
  26:     0x7f50c66267a0 - driver::run::closure.145379
  27:     0x7f50c5d81370 - task::TaskBuilder<S>::try_future::closure.103636
  28:     0x7f50c5d81160 - task::TaskBuilder<S>::spawn_internal::closure.103607
  29:     0x7f50c5a4c1a0 - task::NativeSpawner.Spawner::spawn::closure.8435
  30:     0x7f50c575ae30 - rust_try_inner
  31:     0x7f50c575ae20 - rust_try
  32:     0x7f50c56ff5e0 - unwind::try::h8c75b93d8c87f5c4xGd
  33:     0x7f50c56ff470 - task::Task::run::h3855d187b4c0788fnMc
  34:     0x7f50c5a4bee0 - task::NativeSpawner.Spawner::spawn::closure.8373
  35:     0x7f50c5700cd0 - thread::thread_start::he45c6d58df77cc88C7c
  36:     0x7f50c0591250 - start_thread
  37:     0x7f50c53db3b9 - clone
  38:                0x0 - <unknown>

Could not compile `lsystem`.

Caused by:
  Process didn't exit successfully: `rustc /home/martin/devel/rust/lsystem/src/main.rs --crate-name main --crate-type bin -g --out-dir /home/martin/devel/rust/lsystem/target --dep-info /home/martin/devel/rust/lsystem/target/.fingerprint/lsystem-7b595b16559fa8a0/dep-bin-main -L /home/martin/devel/rust/lsystem/target -L /home/martin/devel/rust/lsystem/target/deps` (status=101)