transform (coroutines): undef task handle in call to closure

[asdine]

func foo() {
	ch := make(chan int)

	fn := func(nb int) {
		ch <- nb
	}

	go func() {
		fn(10)
	}()

	fmt.Println(<-ch)
}

func main() {
  foo()
}

This causes the following compilation error:

async function exp.foo$1 used as function pointer

The same happens when I replace the fn closure by a method.

I compiled to wasm using the 0.12.0 docker image with the following params:

docker run ... \
    tinygo/tinygo:0.12.0 tinygo build -o /dist/exp.wasm -target wasm --no-debug exp

[niaow]

On the current development branch, that part seems to have been fixed an replaced by a different problem: it now segfaults.

[niaow]

tail call void @"/tmp/indirectasync.go.foo$1"(i64 10, i8* nonnull %ch, i8* undef)

It appears that we are passing in an undefined task handle, which is causing a segfault when we attempt to update the state.

[niaow]

v0.13 is getting close to release, so the fix is probably going to have to be pushed back into the next release window.

[niaow]

Alright, I found the cause of the problem:

tinygo/transform/func-lowering.go

Line 147 in 5308e89

funcPtr := builder.CreateSelect(isnil, funcPtrNil, functions[0].funcPtr, "")

This causes the pass to leave behind an indirect function call, which causes the coroutine lowering pass to fail to detect the call. As a result, the call is not lowered, and the parent handle is not provided.