a less-than-helpful error span

option::none

(gdb) bt
#0  upcall_fail (expr=0x103a1e910 "option none", file=0x10124f3c0 "src/rustc/rustc.rc", line=1) at rust_upcall.cpp:129
#1  0x0000000100c86e5a in option::get2685::_257e517213434599 ()
#2  0x0000000100c86d1a in map::chained::hashmap::get2684::_91be2091be825ddf ()
#3  0x0000000100c82b91 in middle::trans::type_use::type_uses_for::_7f98967a2233a3a9 ()
#4  0x0000000100c572a0 in middle::trans::base::monomorphic_fn::_c2859e914b9cd880 ()
#5  0x0000000100ca3c2f in middle::trans::base::lval_static_fn_inner::_73bc9bc67815ad92 ()
#6  0x0000000100ca3135 in middle::trans::base::lval_static_fn::_edc25cdd3a653ce5 ()
#7  0x0000000100cb0cb2 in middle::trans::base::trans_var::_384be2fad5816f12 ()
#8  0x0000000100cb09aa in middle::trans::base::trans_path::_e04090beddd9c39c ()
#9  0x0000000100cb40b0 in middle::trans::base::trans_callee::_8147dc68fe2dadcc ()
#10 0x0000000100cc3811 in middle::trans::base::trans_call::anon ()
#11 0x0000000100ccec07 in middle::trans::base::trans_call_inner::anon ()
#12 0x0000000100cce9db in middle::trans::base::with_scope::_1e9e241850437bd7 ()
#13 0x0000000100c6a55f in middle::trans::base::trans_call_inner::_937aed1df954472e ()
#14 0x0000000100cc3514 in middle::trans::base::trans_call::_2ed6787ab2343f0f ()
#15 0x0000000100c6dcdc in middle::trans::base::trans_expr::_bb28e87fa51144c6 ()
#16 0x0000000100c7228f in middle::trans::base::trans_expr_save_in::_fce7ad71255a1f98 ()
#17 0x0000000100cdc63b in middle::trans::base::init_local::_179bd74e13a21a4f ()
#18 0x0000000100cdfcd2 in middle::trans::base::trans_stmt::anon ()
#19 0x0000000100c161e1 in vec::each1700::_557883d14925caad ()
#20 0x0000000100cdf9b7 in middle::trans::base::trans_stmt::_c3b9c0cd1f39e096 ()
#21 0x0000000100ce4b9d in middle::trans::base::trans_block::anon ()
#22 0x0000000100c161e1 in vec::each1700::_557883d14925caad ()
#23 0x0000000100c7bf48 in middle::trans::base::trans_block::_ed6690bac6e63cc5 ()
#24 0x0000000100cea63e in middle::trans::base::trans_closure::_6e2e724452d99999 ()
#25 0x0000000100c94600 in middle::trans::base::trans_fn::_99f997df435a9583 ()
#26 0x0000000100c9fed8 in middle::trans::base::trans_item::_3bdf284a94b9615f ()
#27 0x0000000100cf13aa in middle::trans::base::trans_mod::anon ()
#28 0x0000000100c161e1 in vec::each1700::_557883d14925caad ()
#29 0x0000000100cf09af in middle::trans::base::trans_mod::_45bb27e0deafb644 ()
#30 0x0000000100d05289 in middle::trans::base::trans_crate::_a188b535c56a1ff3 ()
#31 0x00000001011c82d5 in driver::driver::compile_upto::thunk22369 ()
#32 0x00000001011c72a8 in driver::driver::time22351::_795cc813b0c6f9bb ()
#33 0x00000001011bfa20 in driver::driver::compile_upto::_283c8285774f3aaa ()
#34 0x00000001011c8bdf in driver::driver::compile_input::_c7ffb185ccd6a3f9 ()
#35 0x0000000100004794 in run_compiler::_316abe6092506b73 ()
#36 0x000000010000db9b in main::anon ()
#37 0x000000010000ce8c in monitor::anon ()
#38 0x000000010000bf52 in task::try312::anon ()
#39 0x000000010008ca99 in task::spawn_raw::anon ()
#40 0x0000000101670105 in task_start_wrapper (a=0x103a1e910) at rust_task.cpp:141