rustdoc: implementing trait with associated const for primitive causes panic (regression)

[Jascha-N]

Nightly rustdoc seems to panic when implementing a trait with an associated const for a primitive type.

Reduced test case:

#![feature(associated_consts)]

pub trait Foo {
    const BAR: usize;
}

impl Foo for () {
    const BAR: usize = 0;
}

Message:
thread '<unnamed>' panicked at 'called Option::unwrap()on aNone value', ../src/libcore\option.rs:330

Meta

>rustdoc -vV
rustdoc 1.8.0-nightly (57c357d89 2016-02-16)
binary: rustdoc
commit-hash: 57c357d89183df173b0e42a0f745d9cfdb67fb1a
commit-date: 2016-02-16
host: x86_64-pc-windows-msvc
release: 1.8.0-nightly

Backtrace:

   0:     0x7ffc6b5cd947 - panicking::Location<'a>::line::hd292ced6adc3cf6b7fz
   1:     0x7ffc6b5cd146 - panicking::take_handler::h49f661ca9b556367Wdz
   2:     0x7ffc6b59410f - sys_common::unwind::begin_unwind_inner::h72177c2eb1fe6c2eLct
   3:     0x7ffc6b594b9d - sys_common::unwind::begin_unwind_fmt::h9befc5f9bdb15c19Rbt
   4:     0x7ffc6b5c2f82 - rust_begin_unwind
   5:     0x7ffc6b5daac8 - panicking::panic_fmt::h8430b6988b78563f6YL
   6:     0x7ffc6b5db3c0 - panicking::panic::h331ae34734277dc3DXL
   7:     0x7ffc669c128e - html::render::Cache.DocFolder::fold_item::h467e95350f348073Q5o
   8:     0x7ffc6684b7d1 - html::render::run::h9521371f3809b50bX8n
   9:     0x7ffc6682626a - main_args::h6d07868c1334373bU3u
  10:     0x7ffc66822751 - main::hf5a3402ea1356a63GZu
  11:     0x7ffc6b5c2eb8 - sys_common::thread_local::Key.Drop::drop::h122da565f997e58984s
  12:     0x7ffc6b5bc7f2 - sys_common::unwind::inner_try::h6f3bf9f042fec881N9s
  13:     0x7ffc66822cdf - main::hf5a3402ea1356a63GZu
  14:     0x7ffc6b5cb62b - sys::process::Command::cwd::h2628fdc5c60e66846Sx
  15:     0x7ffc860f8101 - BaseThreadInitThunk

[Jascha-N]

The last nightly version that documented the above code successfully is:

>rustc -vV
rustc 1.8.0-nightly (ce4b75f25 2016-02-12)
binary: rustc
commit-hash: ce4b75f25662cb9facafc4bef368410a2979b936
commit-date: 2016-02-12
host: x86_64-pc-windows-msvc
release: 1.8.0-nightly

I've narrowed the breakage down to one of the following commits: a085e3b, 938202c, 5c98ae3.