Building `ring` with a rustc with debug assertions enabled ICEs

[oli-obk]

The overflow triggers in

rust/src/libsyntax/parse/parser.rs

Line 1187 in 1005f3b

self.unmatched_angle_bracket_count -= 1;

cc @estebank

stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:39
   1: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:70
             at src/libstd/sys_common/backtrace.rs:58
   2: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:200
   3: std::panicking::default_hook
             at src/libstd/panicking.rs:215
   4: rustc::util::common::panic_hook
             at src/librustc/util/common.rs:39
   5: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:482
   6: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:385
   7: rust_begin_unwind
             at src/libstd/panicking.rs:312
   8: core::panicking::panic_fmt
             at src/libcore/panicking.rs:85
   9: core::panicking::panic
             at src/libcore/panicking.rs:49
  10: syntax::parse::parser::Parser::expect_gt
             at src/libsyntax/parse/parser.rs:1187
  11: syntax::parse::parser::Parser::parse_path_segment
             at src/libsyntax/parse/parser.rs:2389
  12: syntax::parse::parser::Parser::parse_path_segments
             at src/libsyntax/parse/parser.rs:2324
  13: syntax::parse::parser::Parser::parse_path_common
             at src/libsyntax/parse/parser.rs:2292
  14: syntax::parse::parser::Parser::parse_ty_common
             at src/libsyntax/parse/parser.rs:2273
             at src/libsyntax/parse/parser.rs:1757
  15: syntax::parse::parser::Parser::parse_item_implementation
             at src/libsyntax/parse/parser.rs:1622
             at src/libsyntax/parse/parser.rs:6647
             at src/libsyntax/parse/parser.rs:7925
  16: syntax::parse::parser::Parser::collect_tokens
             at src/libsyntax/parse/parser.rs:7712
             at src/libsyntax/parse/parser.rs:8331
  17: syntax::parse::parser::Parser::parse_item_
             at src/libsyntax/parse/parser.rs:7711
  18: syntax::ext::expand::<impl syntax::parse::parser::Parser<'a>>::parse_ast_fragment
             at src/libsyntax/parse/parser.rs:8373
             at src/libsyntax/ext/expand.rs:990
  19: syntax::ext::tt::macro_rules::ParserAnyMacro::make
             at src/libsyntax/ext/tt/macro_rules.rs:47
  20: syntax::ext::expand::<impl syntax::ext::base::MacResult for syntax::ext::tt::macro_rules::ParserAnyMacro<'a>>::make_items
             at src/libsyntax/ext/expand.rs:136
  21: syntax::ext::expand::AstFragmentKind::make_from
             at src/libsyntax/ext/expand.rs:72
  22: syntax::ext::expand::MacroExpander::expand_invoc
             at src/libsyntax/ext/expand.rs:786
             at src/libsyntax/ext/expand.rs:521
  23: syntax::ext::expand::MacroExpander::expand_fragment
             at src/libsyntax/ext/expand.rs:354
  24: syntax::ext::expand::MacroExpander::expand_crate
             at src/libsyntax/ext/expand.rs:281
  25: rustc_driver::driver::phase_2_configure_and_expand_inner::{{closure}}
             at src/librustc_driver/driver.rs:979
             at /home/oliver/Projects/rust/rust3/src/librustc/util/common.rs:150
             at /home/oliver/Projects/rust/rust3/src/librustc/util/common.rs:144
             at src/librustc_driver/driver.rs:978
  26: rustc::util::common::time
             at /home/oliver/Projects/rust/rust3/src/librustc/util/common.rs:150
             at /home/oliver/Projects/rust/rust3/src/librustc/util/common.rs:144
  27: rustc_driver::driver::phase_2_configure_and_expand
             at src/librustc_driver/driver.rs:932
             at src/librustc_driver/driver.rs:745
  28: rustc_driver::driver::compile_input
             at src/librustc_driver/driver.rs:174
  29: rustc_driver::run_compiler_with_pool
             at src/librustc_driver/lib.rs:524
  30: <scoped_tls::ScopedKey<T>>::set
             at src/librustc_driver/lib.rs:446
             at src/librustc_driver/driver.rs:65
             at /home/oliver/.cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-0.1.2/src/lib.rs:155
  31: rustc_driver::run_compiler
             at src/librustc_driver/driver.rs:64
             at src/librustc_driver/lib.rs:445
  32: <scoped_tls::ScopedKey<T>>::set
             at src/librustc_driver/lib.rs:1647
             at src/librustc_driver/lib.rs:168
             at /home/oliver/.cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-0.1.2/src/lib.rs:155
             at /home/oliver/Projects/rust/rust3/src/libsyntax/lib.rs:101
             at /home/oliver/.cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-0.1.2/src/lib.rs:155
query stack during panic:
end of query stack