Runtime crash when using async let variables

[AndrewBarba]

When await-ing an async let variable, the process crashes:

Feb 10 17:02:17.399  INFO Listening on http://127.0.0.1:7676
Feb 10 17:02:19.866  INFO request{id=0}: handling request GET http://127.0.0.1:7676/
Feb 10 17:02:19.871  INFO request{id=0}: request completed using 3.5 MB of WebAssembly heap
Feb 10 17:02:19.871  INFO request{id=0}: request completed in 4.967166ms
Feb 10 17:02:19.871 ERROR request{id=0}: WebAssembly trapped: wasm trap: indirect call type mismatch
wasm backtrace:
    0: 0x870b4b - <unknown>!task_future_wait_resume_adapter(swift::AsyncContext*)

This stack is generated from a Swift application running in Viceroy but I expect the crash is the same in any Wasm runtime (Wasmtime, Wasmer, etc.). Note: the crash does not happen if I create async let variables but never await them.

[MaxDesiatov]

cc @kateinoigakukun

[MaxDesiatov]

@AndrewBarba is this reproducible for you with any of the latest dev snapshots, for example this one? https://github.com/swiftwasm/swift/releases/tag/swift-wasm-DEVELOPMENT-SNAPSHOT-2022-02-12-a

[kateinoigakukun]

Here is a minimum reproducible snippet.

func getX() async -> Int { return 0 }

@_optimize(none)
func blackhole<T>(_: T) {}

@main
struct Entrypoint {
  static func main() async {
    async let x = getX()
    blackhole(await x)
  }
}

$ /home/katei/.ghq/work.katei.dev/swiftwasm-source/dist-toolchain-sdk/swift-wasm-DEVELOPMENT-SNAPSHOT-2022-02-14-a/usr/bin/swiftc -target wasm32-unknown-wasi foo.swift -parse-as-library -o foo.wasm
$ wasmtime main.wasm
Error: failed to run main module `main.wasm`

Caused by:
    0: failed to invoke command default
    1: wasm trap: indirect call type mismatch
       wasm backtrace:
           0: 0x395c36 - <unknown>!task_future_wait_resume_adapter(swift::AsyncContext*)
           1: 0x39344e - <unknown>!swift::runJobInEstablishedExecutorContext(swift::Job*)
           2: 0x393c1b - <unknown>!swift_job_run
           3: 0x3950a9 - <unknown>!swift_task_donateThreadToGlobalExecutorUntil
           4: 0x3968c5 - <unknown>!swift_task_asyncMainDrainQueueImpl()
           5: 0x396892 - <unknown>!swift_task_asyncMainDrainQueue
           6: 0xf39d - <unknown>!main
           7: 0x3d1bf6 - <unknown>!main
           8: 0x3d1c72 - <unknown>!__main_void
           9: 0x3d1bb7 - <unknown>!__original_main
          10: 0xe4c3 - <unknown>!_start

katei@yama:/tmp/tmp.lEoJtsayOF$ wasminspect main.wasm
[2022-02-14T17:44:55Z WARN  wasminspect_debugger] Failed to load dwarf info: no .debug_str
(wasminspect) run
Function exec failure indirect call type mismatch for '$s4main10EntrypointVAAyyYaFZTY1_':
 >> call_indirect instruction expected FuncType { params: [I32, I32, I32], returns: [] }
 >> but actual implementation has      FuncType { params: [I32, I32, I32, I32], returns: [] }
(wasminspect)