wasm-pack build --dev panicked at 'assertion failed: !self.dead.contains(&id)'

[MaulingMonkey]

🐛 Bug description

wasm-pack build --dev panics inside walrus's tombstone_arena. It shouldn't.

👟 Steps to reproduce

git clone https://github.com/MaulingMonkey/rust_wasm_sample.git
cd rust_wasm_sample
git checkout ff3bbedbcf3b717a0ae
wasm-pack build --dev

(Github view of the checkout: ff3bbedbcf3b717a0ae)

I've been having trouble figuring out how to get a useful stack backtrace out of wasm-pack, if you have suggestions I'll be happy to rerun.

HEAD is now at ff3bbed Add bin version, scripts for dual native/wasm builds.
[INFO]: Checking for the Wasm target...
[INFO]: Compiling to Wasm...
    Finished dev [unoptimized + debuginfo] target(s) in 0.04s
[INFO]: Installing wasm-bindgen...
thread 'main' panicked at 'assertion failed: !self.dead.contains(&id)', C:\Program Files\Rust\.cargo\registry\src\github.com-1ecc6299db9ec823\walrus-0.8.0\src\tombstone_arena.rs:139:9
stack backtrace:
   0: <unknown>
   1: <unknown>
   2: <unknown>
   3: <unknown>
   4: <unknown>
   5: <unknown>
   6: <unknown>
   7: <unknown>
   8: <unknown>
   9: <unknown>
  10: <unknown>
  11: <unknown>
  12: <unknown>
  13: <unknown>
  14: <unknown>
  15: BaseThreadInitThunk
  16: RtlUserThreadStart
Error: Running the wasm-bindgen CLI
Caused by: failed to execute `wasm-bindgen`: exited with exit code: 101

Misc. notes:

• wasm-pack build (without the --dev flag) works.
• wasm-pack build --dev stops panicing after MaulingMonkey/rust_wasm_sample@0def95e

🌍 Your environment

wasm-pack version: 0.8.1
rustc version: rustc 1.35.0 (3c235d560 2019-05-20)
toolchain: stable-x86_64-pc-windows-msvc

[MaulingMonkey]

Ahh, this is actually a wasm-bindgen bug, not a wasm-pack one. Will refile with more info there...
EDIT: Refiled @ rustwasm/wasm-bindgen#1613