Rust doesn't build in debug mode

[Manishearth]

https://gist.github.com/GuillaumeGomez/63280240ff65fdff6a6e

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: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/snap3-linux/build/src/libsyntax/diagnostic.rs:129

stack backtrace:
1: 0x931c37c0 - sys::backtrace::write::h6e1a16e5b491c0f3O8z
2: 0x931d23b0 - panicking::on_panic::ha15f2f8740ed7a6fQ3I
3: 0x9318a330 - rt::unwind::begin_unwind_inner::ha6405b1772621526jKI
4: 0x92f25c90 - rt::unwind::begin_unwind::h3132232555169189115
5: 0x92f25c20 - diagnostic::SpanHandler::span_bug::h35fee2453f651c90UBD
6: 0x91914d70 - session::Session::span_bug::h70107cb3e0d3f2ddTdp
7: 0x916834f0 - trans::debuginfo::scope_metadata::h9006c031a88e845ah6D
8: 0x915aa8e0 - trans::debuginfo::set_source_location::h5fcedf96480408c0xzD
9: 0x91564010 - trans::expr::trans_into::h22c2538f2e3eccadmnh
10: 0x91564010 - trans::expr::trans_into::h22c2538f2e3eccadmnh
11: 0x915bfbd0 - trans::expr::trans_uniq_expr::h0522e109aa920b5djkj
12: 0x915c0850 - trans::expr::trans_unary::h7a9d8850d4eb6facygj
13: 0x915ac3d0 - trans::expr::trans_unadjusted::h052d761dcea41eb1m4h
14: 0x91564010 - trans::expr::trans_into::h22c2538f2e3eccadmnh
15: 0x915e0560 - trans::expr::trans_adt::haae68323d8da1410C6i
16: 0x915e2b30 - trans::expr::trans_struct::closure.42393
17: 0x915ca5f0 - trans::expr::trans_struct::h55b354ec0c149d60y2i
18: 0x915acfe0 - trans::expr::trans_rvalue_dps_unadjusted::hf11cf7ef5b8cdf77Szi
19: 0x91564010 - trans::expr::trans_into::h22c2538f2e3eccadmnh
20: 0x91564b80 - trans::controlflow::trans_block::hbfe58d62c396d6e1U4d
21: 0x9162d750 - trans::base::trans_closure::hdb71213f3abe859acat
22: 0x915514f0 - trans::base::trans_fn::h547c5461a296c1965kt
23: 0x91551a50 - trans::monomorphize::monomorphic_fn::h0d0d12912e5e7d20csd
24: 0x915910c0 - trans::callee::trans_fn_ref_with_substs::h79ddfa4cda7814f81kg
25: 0x9158fb90 - trans::callee::trans_fn_ref::h9575eadfdeacfc19B9f
26: 0x9158ceb0 - trans::callee::trans::h33b83f676ff222efSYf
27: 0x915a2f90 - trans::callee::trans_call_inner::h10174427473090758353
28: 0x915acfe0 - trans::expr::trans_rvalue_dps_unadjusted::hf11cf7ef5b8cdf77Szi
29: 0x91564010 - trans::expr::trans_into::h22c2538f2e3eccadmnh
30: 0x915e0560 - trans::expr::trans_adt::haae68323d8da1410C6i
31: 0x915e2b30 - trans::expr::trans_struct::closure.42393
32: 0x915ca5f0 - trans::expr::trans_struct::h55b354ec0c149d60y2i
33: 0x915acfe0 - trans::expr::trans_rvalue_dps_unadjusted::hf11cf7ef5b8cdf77Szi
34: 0x91564010 - trans::expr::trans_into::h22c2538f2e3eccadmnh
35: 0x91663330 - trans::_match::mk_binding_alloca::h3698673747715730836
36: 0x91563750 - trans::base::init_local::h9e59737bbb5cd63fsns
37: 0x91564b80 - trans::controlflow::trans_block::hbfe58d62c396d6e1U4d
38: 0x9162d750 - trans::base::trans_closure::hdb71213f3abe859acat
39: 0x915514f0 - trans::base::trans_fn::h547c5461a296c1965kt
40: 0x91551a50 - trans::monomorphize::monomorphic_fn::h0d0d12912e5e7d20csd
41: 0x915910c0 - trans::callee::trans_fn_ref_with_substs::h79ddfa4cda7814f81kg
42: 0x9158fb90 - trans::callee::trans_fn_ref::h9575eadfdeacfc19B9f
43: 0x9158ceb0 - trans::callee::trans::h33b83f676ff222efSYf
44: 0x915a2f90 - trans::callee::trans_call_inner::h10174427473090758353
45: 0x915acfe0 - trans::expr::trans_rvalue_dps_unadjusted::hf11cf7ef5b8cdf77Szi
46: 0x915ac3d0 - trans::expr::trans_unadjusted::h052d761dcea41eb1m4h
47: 0x91565650 - trans::expr::trans::h764b257c73d7b82duth
48: 0x9159d0e0 - trans::callee::trans_args::h0a23076c699a15a2a1g
49: 0x915a2f90 - trans::callee::trans_call_inner::h10174427473090758353
50: 0x915acfe0 - trans::expr::trans_rvalue_dps_unadjusted::hf11cf7ef5b8cdf77Szi
51: 0x915ac3d0 - trans::expr::trans_unadjusted::h052d761dcea41eb1m4h
52: 0x91565650 - trans::expr::trans::h764b257c73d7b82duth
53: 0x9159d0e0 - trans::callee::trans_args::h0a23076c699a15a2a1g
54: 0x915a2f90 - trans::callee::trans_call_inner::h10174427473090758353
55: 0x915acfe0 - trans::expr::trans_rvalue_dps_unadjusted::hf11cf7ef5b8cdf77Szi
56: 0x91564010 - trans::expr::trans_into::h22c2538f2e3eccadmnh
57: 0x91663330 - trans::_match::mk_binding_alloca::h3698673747715730836
58: 0x91563750 - trans::base::init_local::h9e59737bbb5cd63fsns
59: 0x91564b80 - trans::controlflow::trans_block::hbfe58d62c396d6e1U4d
60: 0x915acfe0 - trans::expr::trans_rvalue_dps_unadjusted::hf11cf7ef5b8cdf77Szi
61: 0x91564010 - trans::expr::trans_into::h22c2538f2e3eccadmnh
62: 0x9164b570 - trans::_match::trans_match_inner::h9674fc66f725fbeb4ww
63: 0x915acfe0 - trans::expr::trans_rvalue_dps_unadjusted::hf11cf7ef5b8cdf77Szi
64: 0x915ac3d0 - trans::expr::trans_unadjusted::h052d761dcea41eb1m4h
65: 0x91565650 - trans::expr::trans::h764b257c73d7b82duth
66: 0x91563750 - trans::base::init_local::h9e59737bbb5cd63fsns
67: 0x91564b80 - trans::controlflow::trans_block::hbfe58d62c396d6e1U4d
68: 0x9162d750 - trans::base::trans_closure::hdb71213f3abe859acat
69: 0x915514f0 - trans::base::trans_fn::h547c5461a296c1965kt
70: 0x91551a50 - trans::monomorphize::monomorphic_fn::h0d0d12912e5e7d20csd
71: 0x915910c0 - trans::callee::trans_fn_ref_with_substs::h79ddfa4cda7814f81kg
72: 0x915a6060 - trans::meth::trans_method_callee::hf0207e1e2fdfc9e9fVx
73: 0x915a47e0 - trans::callee::trans_call_inner::h2563465562787626030
74: 0x915acfe0 - trans::expr::trans_rvalue_dps_unadjusted::hf11cf7ef5b8cdf77Szi
75: 0x91564010 - trans::expr::trans_into::h22c2538f2e3eccadmnh
76: 0x915e0560 - trans::expr::trans_adt::haae68323d8da1410C6i
77: 0x915e2b30 - trans::expr::trans_struct::closure.42393
78: 0x915ca5f0 - trans::expr::trans_struct::h55b354ec0c149d60y2i
79: 0x915acfe0 - trans::expr::trans_rvalue_dps_unadjusted::hf11cf7ef5b8cdf77Szi
80: 0x91564010 - trans::expr::trans_into::h22c2538f2e3eccadmnh
81: 0x91564b80 - trans::controlflow::trans_block::hbfe58d62c396d6e1U4d
82: 0x9162d750 - trans::base::trans_closure::hdb71213f3abe859acat
83: 0x915514f0 - trans::base::trans_fn::h547c5461a296c1965kt
84: 0x9154d080 - trans::base::trans_item::h59f500effe25e65aXIt
85: 0x9154d080 - trans::base::trans_item::h59f500effe25e65aXIt
86: 0x9154d080 - trans::base::trans_item::h59f500effe25e65aXIt
87: 0x91635150 - trans::base::trans_crate::h9a17df2c0522669exEu
88: 0x914625b0 - driver::phase_4_translate_to_llvm::h15627d7b481f533fnNa
89: 0x9143cb30 - driver::compile_input::hae572d9f5da36b40Gba
90: 0x91506ad0 - run_compiler::hf3a8885919a54fb8z5b
91: 0x915053d0 - thunk::F.Invoke<A, R>::invoke::h3212378312878711274
92: 0x915042c0 - rt::unwind::try::try_fn::h15521701545948476290
93: 0x931d6fd0 - rust_try_inner
94: 0x931d6fc0 - rust_try
95: 0x915045c0 - thunk::F.Invoke<A, R>::invoke::h14398411544942163491
96: 0x931d10f0 - sys::thread::thread_start::hc259f128b70f294f3wE
97: 0x943a60c0 - start_thread
98: 0x94fde449 - __clone
99: 0x0 - <unknown>

make: *** [x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib/stamp.std] 

cc @GuillaumeGomez @michaelwoerister

[jdm]

Dup of #22432.