Repository: rust
Issue: integer overflow in parser angle bracket handling
Labels: I-ICE,A-parser,T-compiler,C-bug,requires-debug-assertions

the parser uses a `u16` to track angle brackets. This isn't exactly unreasonable, but not everyone writes reasonable code. Some people don't, and this makes the compiler sad. It should probably be a `u32`.

https://github.com/boltlabs-inc/dialectic/tree/0d545aceb4a204b4d412e8fcf877ff2a41e35c3b/dialectic-macro

I expected to see this happen: no integer overflow
Instead, this happened: integer overflow

https://crater-reports.s3.amazonaws.com/pr-119440-1/try%23fe8f664b41f030f307cfeb6cb8c3a1419292aeed/reg/dialectic-macro-0.1.0/log.txt

### Meta
`rustc --version --verbose`:
```
roughly rustc 1.77.0-nightly (3cdd004e5 2023-12-29)
```

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<details><summary>Backtrace</summary>
<p>

```
[INFO] [stderr] thread 'rustc' panicked at compiler/rustc_parse/src/parser/mod.rs:740:13:
[INFO] [stderr] attempt to add with overflow
[INFO] [stderr] stack backtrace:
[INFO] [stderr]    0:     0x7fc9fab8b946 - std::backtrace_rs::backtrace::libunwind::trace::h5f2f9ef1f20601b2
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
[INFO] [stderr]    1:     0x7fc9fab8b946 - std::backtrace_rs::backtrace::trace_unsynchronized::h0afa123c60ac3544
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
[INFO] [stderr]    2:     0x7fc9fab8b946 - std::sys_common::backtrace::_print_fmt::h6bf637b081885c8e
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/sys_common/backtrace.rs:68:5
[INFO] [stderr]    3:     0x7fc9fab8b946 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h2c6761a2e200c979
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/sys_common/backtrace.rs:44:22
[INFO] [stderr]    4:     0x7fc9fabde060 - core::fmt::rt::Argument::fmt::h16857210251b8080
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/core/src/fmt/rt.rs:142:9
[INFO] [stderr]    5:     0x7fc9fabde060 - core::fmt::write::h15e31c36c28ee02f
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/core/src/fmt/mod.rs:1120:17
[INFO] [stderr]    6:     0x7fc9fab7f2df - std::io::Write::write_fmt::h30eda9caba94b19c
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/io/mod.rs:1810:15
[INFO] [stderr]    7:     0x7fc9fab8b724 - std::sys_common::backtrace::_print::h83083a5d53637ec4
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/sys_common/backtrace.rs:47:5
[INFO] [stderr]    8:     0x7fc9fab8b724 - std::sys_common::backtrace::print::hc98591726bef92fd
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/sys_common/backtrace.rs:34:9
[INFO] [stderr]    9:     0x7fc9fab8e4b7 - std::panicking::default_hook::{{closure}}::hc8badbdd77cc4572
[INFO] [stderr]   10:     0x7fc9fab8e219 - std::panicking::default_hook::ha24461576e8ae120
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/panicking.rs:292:9
[INFO] [stderr]   11:     0x7fc9fdaa28ac - std[9f4ae9e9cff43acb]::panicking::update_hook::<alloc[acd61960e0df7531]::boxed::Box<rustc_driver_impl[d22198136dec6837]::install_ice_hook::{closure#0}>>::{closure#0}
[INFO] [stderr]   12:     0x7fc9fab8ec06 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h55151e58e7322d9e
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/alloc/src/boxed.rs:2029:9
[INFO] [stderr]   13:     0x7fc9fab8ec06 - std::panicking::rust_panic_with_hook::hed55d523c6a2382e
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/panicking.rs:783:13
[INFO] [stderr]   14:     0x7fc9fab8e919 - std::panicking::begin_panic_handler::{{closure}}::h944452fa41308f37
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/panicking.rs:649:13
[INFO] [stderr]   15:     0x7fc9fab8be46 - std::sys_common::backtrace::__rust_end_short_backtrace::h91d397e41fb21da0
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/sys_common/backtrace.rs:171:18
[INFO] [stderr]   16:     0x7fc9fab8e6b0 - rust_begin_unwind
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/std/src/panicking.rs:645:5
[INFO] [stderr]   17:     0x7fc9fabda765 - core::panicking::panic_fmt::he0a5a6033f24be27
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/core/src/panicking.rs:72:14
[INFO] [stderr]   18:     0x7fc9fabda823 - core::panicking::panic::hc85da36c3a268157
[INFO] [stderr]                                at /rustc/fe8f664b41f030f307cfeb6cb8c3a1419292aeed/library/core/src/panicking.rs:144:5
[INFO] [stderr]   19:     0x7fc9ff34c9ac - <rustc_parse[951bc98562c6db9b]::parser::Parser>::eat_lt
[INFO] [stderr]   20:     0x7fc9ff25d7c5 - <rustc_parse[951bc98562c6db9b]::parser::Parser>::parse_path_inner
[INFO] [stderr]   21:     0x7fc9ff4c65c2 - <rustc_parse[951bc98562c6db9b]::parser::Parser>::parse_ty_common
[INFO] [stderr]   22:     0x7fc9ff351a03 - <rustc_parse[951bc98562c6db9b]::parser::Parser>::parse_angle_args
[INFO] [stderr]   23:     0x7fc9ff25d81e - <rustc_parse[951bc98562c6db9b]::parser::Parser>::parse_path_inner
<snip snip snip>
```

</p>
</details>