Wasm: Panic trying to make exported function async

[asdine]

The compiler panics trying to compile what it appears to be functions that expect other functions.

Target: wasm
Tinygo version: Docker version of 0.15.0

Stacktrace:

panic: trying to make exported function async: (github.com/genjidb/genji/document.Stream).Iterate$invoke

goroutine 1 [running]:
github.com/tinygo-org/tinygo/transform.(*coroutineLoweringPass).findAsyncFuncs(0xc008591040)
        /home/circleci/project/transform/coroutines.go:186 +0xa64
github.com/tinygo-org/tinygo/transform.(*coroutineLoweringPass).load(0xc008591040, 0x20, 0x9a16790)
        /home/circleci/project/transform/coroutines.go:305 +0x36c
github.com/tinygo-org/tinygo/transform.LowerCoroutines(0x8be16c0, 0x8be1601, 0x0, 0x0)
        /home/circleci/project/transform/coroutines.go:70 +0x15f
github.com/tinygo-org/tinygo/transform.Optimize(0x8be16c0, 0xc000336060, 0x2, 0x2, 0x5, 0x0, 0x0, 0x0)
        /home/circleci/project/transform/optimizer.go:120 +0xef0
github.com/tinygo-org/tinygo/builder.Build(0x7ffd9a4f9efb, 0x21, 0x7ffd9a4f9ed2, 0x10, 0xc000336060, 0xc008591ba8, 0x0, 0x0)
        /home/circleci/project/builder/build.go:109 +0x337a
main.Build(0x7ffd9a4f9efb, 0x21, 0x7ffd9a4f9ed2, 0x10, 0xc000300000, 0x0, 0x12)
        /home/circleci/project/main.go:94 +0xc5
main.main()
        /home/circleci/project/main.go:856 +0x1f96

Besides the error and the stacktrace above, it is impossible for me to write a simple code sample for you to reproduce it because the behavior of the compiler is really difficult to grasp: Two statements cause the compiler to fail, but if I use statement A or statement B separately, the compilation succeeds. If you have any tips on how I could debug this more efficiently I will try to give more details.

[aykevl]

This looks like a duplicate of #733 so closing this issue in favor of it.