package main

type StateMachine[T any] struct {
	data *T
}

func NewStateMachine[T any](data *T) *StateMachine[T] {
	return &StateMachine[T]{data: data}
}

func UpdateState[T any](m *StateMachine[T], fn func(data *T)) {
	fn(m.data)
}

type StateFoo[T any] struct {
	Bar      string
	SubState T
}

func NewFoo[T any]() *Foo[T] {
	return &Foo[T]{
		StateMachine: NewStateMachine(&StateFoo[T]{
			Bar: "",
		}),
	}
}

type Foo[T any] struct {
	StateMachine *StateMachine[StateFoo[T]]
}

func (f *Foo[T]) Update(fn func(*StateFoo[T])) {
	UpdateState(f.StateMachine, fn)
}

func main() {
	type SubState struct {
		X string
	}
	f := NewFoo[SubState]()
	f.Update(func(foo *StateFoo[SubState]) {})
}

//internal compiler error: assigning m.data (type *go.shape.struct { Bar string; SubState struct { X string } }_0) to parameter <S> (type *StateFoo["".SubState·1])
//internal compiler error: assigning m.data (type *go.shape.struct { Bar string; SubState struct { X string } }_0) to parameter foo (type *StateFoo["".SubState·1])