Exceptions raised from Rust with `error::raise` crash the playground with an unreachable error

[lopopolo]

Exceptions raised in Rust code crash the playground.

Example

Regexp.compile(Object.new)

Integer('0x')

Stacktrace

159ff24693cdf2cbaabe.bundle.js:2 artichoke 0.1.0-pre.0 (2021-02-24 revision 4156) [wasm32-unknown-emscripten]
159ff24693cdf2cbaabe.bundle.js:2 [rustc 1.50.0 (cb75ad5db 2021-02-10) on x86_64-unknown-linux-gnu]
159ff24693cdf2cbaabe.bundle.js:2 Uncaught RuntimeError: unreachable
    at https://artichoke.run/playground.wasm:wasm-function[187]:0x22952
    at dynCall_viii (https://artichoke.run/playground.wasm:wasm-function[3052]:0x1fa79a)
    at https://artichoke.run/159ff24693cdf2cbaabe.bundle.js:2:2437295
    at invoke_viii (https://artichoke.run/159ff24693cdf2cbaabe.bundle.js:2:2502225)
    at https://artichoke.run/playground.wasm:wasm-function[1695]:0x120ede
    at https://artichoke.run/playground.wasm:wasm-function[1696]:0x121526
    at https://artichoke.run/playground.wasm:wasm-function[1353]:0xdd4e9
    at https://artichoke.run/playground.wasm:wasm-function[188]:0x229ee
    at dynCall_viii (https://artichoke.run/playground.wasm:wasm-function[3052]:0x1fa79a)
    at https://artichoke.run/159ff24693cdf2cbaabe.bundle.js:2:2437295

[lopopolo]

discovered while working on artichoke/artichoke#1107.

[lopopolo]

I think these upstream mruby PRs might be related since the crashes occur when raising errors in native code:

• Introducing the mrb_protect_raw() API function mruby/mruby#5415
• mruby/mruby@1a82bab

[lopopolo]

this still reproduces as of 4c9fac2