unsafe.go

package main

var x interface{ f() }

type A struct {
	fp func()
}

func (a A) f() { a.fp() }

type B struct {
	i uint64
}

func (b B) f() {}

func main() {
	x = A{fp: func() {}}
	done := make(chan struct{})
	go func() {
		for i := 0; i < 1_000_000; i++ {
			x.f()
		}
		done <- struct{}{}
	}()
	go func() {
		for {
			x = A{fp: func() {}}
			x.f()
			x = B{i: 0xaaaaaaaaaaaaaaaa}
			x.f()
		}
	}()
	<-done
}