ICE I got when wiring up XML5

XML5ICE

note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'assertion failed: bpos.to_usize() >= mbc.pos.to_usize() + mbc.bytes', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/codemap.rs:738
 
stack backtrace:
   1:     0x2b43da104b84 - sys::backtrace::write::h5e3efc31357524bax4C
   2:     0x2b43da12d528 - panicking::on_panic::ha90a3694573d0234cjJ
   3:     0x2b43da060b0c - rt::unwind::begin_unwind_inner::hed207b77c3567743tZI
   4:     0x2b43dca0edec - rt::unwind::begin_unwind::h13891512158995194072
   5:     0x2b43dca8bbc8 - codemap::CodeMap::bytepos_to_file_charpos::he35a71cdbcb3d0ce69z
   6:     0x2b43dca8a109 - codemap::CodeMap::lookup_char_pos::h68bd093129a66ec5o1z
   7:     0x2b43dabb9dc8 - trans::debuginfo::set_source_location::h0925e3800f91b422hvD
   8:     0x2b43dabbbffc - trans::expr::trans_unadjusted::h4659782999b10bf9SQh
   9:     0x2b43dab7aa20 - trans::expr::trans::h34a5a50e2b27a7d6jfh
  10:     0x2b43dac5d4b6 - trans::_match::trans_match_inner::h002b257be74944acvpw
  11:     0x2b43dabbdc8c - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  12:     0x2b43dabbc468 - trans::expr::trans_unadjusted::h4659782999b10bf9SQh
  13:     0x2b43dab7aa20 - trans::expr::trans::h34a5a50e2b27a7d6jfh
  14:     0x2b43dac5d4b6 - trans::_match::trans_match_inner::h002b257be74944acvpw
  15:     0x2b43dabbdc8c - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  16:     0x2b43dab790a9 - trans::expr::trans_into::h888aac54f571c11b18g
  17:     0x2b43dab7a0c2 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  18:     0x2b43dabc1909 - trans::expr::trans_rvalue_stmt_unadjusted::h97c05dbcdc1bb54cAgi
  19:     0x2b43dab791c5 - trans::expr::trans_into::h888aac54f571c11b18g
  20:     0x2b43dac5e835 - trans::_match::trans_match_inner::h002b257be74944acvpw
  21:     0x2b43dabbdc8c - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  22:     0x2b43dab790a9 - trans::expr::trans_into::h888aac54f571c11b18g
  23:     0x2b43dab7a0c2 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  24:     0x2b43dac3f608 - trans::base::trans_closure::hbc27ba08f4391b2fB3s
  25:     0x2b43dab63c18 - trans::base::trans_fn::h36a5e575e179f463uet
  26:     0x2b43dab65300 - trans::monomorphize::monomorphic_fn::h4f49a2f198840b39qtd
  27:     0x2b43daba370f - trans::callee::trans_fn_ref_with_substs::h4b1705d94cbada7ev6f
  28:     0x2b43daba1cee - trans::callee::trans_fn_ref::h77533e2a592733d25Uf
  29:     0x2b43dabb55b5 - trans::meth::trans_method_callee::hf8dcce7423259e7bHJx
  30:     0x2b43dabb3d09 - trans::callee::trans_call_inner::h3309309044729649080
  31:     0x2b43dabbd507 - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  32:     0x2b43dab790a9 - trans::expr::trans_into::h888aac54f571c11b18g
  33:     0x2b43dac766e7 - trans::_match::mk_binding_alloca::h9494472984018519847
  34:     0x2b43dab784ed - trans::base::init_local::h2dd64b3754f332e9Fis
  35:     0x2b43dab79d52 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  36:     0x2b43dabbdce1 - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  37:     0x2b43dabbc468 - trans::expr::trans_unadjusted::h4659782999b10bf9SQh
  38:     0x2b43dab7aa20 - trans::expr::trans::h34a5a50e2b27a7d6jfh
  39:     0x2b43dab785c2 - trans::base::init_local::h2dd64b3754f332e9Fis
  40:     0x2b43dab79d52 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  41:     0x2b43dabc1909 - trans::expr::trans_rvalue_stmt_unadjusted::h97c05dbcdc1bb54cAgi
  42:     0x2b43dab791c5 - trans::expr::trans_into::h888aac54f571c11b18g
  43:     0x2b43dab7a0c2 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  44:     0x2b43dabbdbf2 - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  45:     0x2b43dab790a9 - trans::expr::trans_into::h888aac54f571c11b18g
  46:     0x2b43dab7a0c2 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  47:     0x2b43dac3f608 - trans::base::trans_closure::hbc27ba08f4391b2fB3s
  48:     0x2b43dab63c18 - trans::base::trans_fn::h36a5e575e179f463uet
  49:     0x2b43dab65300 - trans::monomorphize::monomorphic_fn::h4f49a2f198840b39qtd
  50:     0x2b43daba370f - trans::callee::trans_fn_ref_with_substs::h4b1705d94cbada7ev6f
  51:     0x2b43daba1cee - trans::callee::trans_fn_ref::h77533e2a592733d25Uf
  52:     0x2b43dabb55b5 - trans::meth::trans_method_callee::hf8dcce7423259e7bHJx
  53:     0x2b43dabb3d09 - trans::callee::trans_call_inner::h3309309044729649080
  54:     0x2b43dabbd507 - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  55:     0x2b43dab790a9 - trans::expr::trans_into::h888aac54f571c11b18g
  56:     0x2b43dab78284 - trans::controlflow::trans_stmt_semi::h68ba53cba2177fe044d
  57:     0x2b43dab79d20 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  58:     0x2b43dac3f608 - trans::base::trans_closure::hbc27ba08f4391b2fB3s
  59:     0x2b43dab63c18 - trans::base::trans_fn::h36a5e575e179f463uet
  60:     0x2b43dab65300 - trans::monomorphize::monomorphic_fn::h4f49a2f198840b39qtd
  61:     0x2b43daba370f - trans::callee::trans_fn_ref_with_substs::h4b1705d94cbada7ev6f
  62:     0x2b43daba1cee - trans::callee::trans_fn_ref::h77533e2a592733d25Uf
  63:     0x2b43dabb55b5 - trans::meth::trans_method_callee::hf8dcce7423259e7bHJx
  64:     0x2b43dabb3d09 - trans::callee::trans_call_inner::h3309309044729649080
  65:     0x2b43dabbd507 - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  66:     0x2b43dab790a9 - trans::expr::trans_into::h888aac54f571c11b18g
  67:     0x2b43dab78284 - trans::controlflow::trans_stmt_semi::h68ba53cba2177fe044d
  68:     0x2b43dab79d20 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  69:     0x2b43dabbdce1 - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  70:     0x2b43dab790a9 - trans::expr::trans_into::h888aac54f571c11b18g
  71:     0x2b43dac5e835 - trans::_match::trans_match_inner::h002b257be74944acvpw
  72:     0x2b43dabbdc8c - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  73:     0x2b43dab790a9 - trans::expr::trans_into::h888aac54f571c11b18g
  74:     0x2b43dab7a0c2 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  75:     0x2b43dabc1909 - trans::expr::trans_rvalue_stmt_unadjusted::h97c05dbcdc1bb54cAgi
  76:     0x2b43dab791c5 - trans::expr::trans_into::h888aac54f571c11b18g
  77:     0x2b43dac5e835 - trans::_match::trans_match_inner::h002b257be74944acvpw
  78:     0x2b43dabbdc8c - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  79:     0x2b43dab790a9 - trans::expr::trans_into::h888aac54f571c11b18g
  80:     0x2b43dac766e7 - trans::_match::mk_binding_alloca::h9494472984018519847
  81:     0x2b43dab784ed - trans::base::init_local::h2dd64b3754f332e9Fis
  82:     0x2b43dab79d52 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  83:     0x2b43dabbdce1 - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  84:     0x2b43dab790a9 - trans::expr::trans_into::h888aac54f571c11b18g
  85:     0x2b43dab78284 - trans::controlflow::trans_stmt_semi::h68ba53cba2177fe044d
  86:     0x2b43dab79d20 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  87:     0x2b43dac3f608 - trans::base::trans_closure::hbc27ba08f4391b2fB3s
  88:     0x2b43dab63c18 - trans::base::trans_fn::h36a5e575e179f463uet
  89:     0x2b43dab6525b - trans::monomorphize::monomorphic_fn::h4f49a2f198840b39qtd
  90:     0x2b43daba370f - trans::callee::trans_fn_ref_with_substs::h4b1705d94cbada7ev6f
  91:     0x2b43daba1cee - trans::callee::trans_fn_ref::h77533e2a592733d25Uf
  92:     0x2b43dab9f90d - trans::callee::trans::he3b858bb196fc595mKf
  93:     0x2b43dabb248b - trans::callee::trans_call_inner::h16989623986616311905
  94:     0x2b43dabbe734 - trans::expr::trans_rvalue_dps_unadjusted::h68f2c48a6a850a8clmi
  95:     0x2b43dab790a9 - trans::expr::trans_into::h888aac54f571c11b18g
  96:     0x2b43dab78284 - trans::controlflow::trans_stmt_semi::h68ba53cba2177fe044d
  97:     0x2b43dab79d20 - trans::controlflow::trans_block::h47b77367f4f617e3R5d
  98:     0x2b43dac3f608 - trans::base::trans_closure::hbc27ba08f4391b2fB3s
  99:     0x2b43dab63c18 - trans::base::trans_fn::h36a5e575e179f463uet
  100:     0x2b43dab5ee0f - trans::base::trans_item::h567bb8e5f2969b88mCt
 ... <frames omitted>

I'm seeing that on my html5ever branch as well :/