// compile package main type Foo interface { Print() } type Bar struct{} func (b Bar) Print() {} func main() { b := make([]Bar, 20) f := make([]Foo, 20) for i := range f { f[i] = b[i] } T(f) _ = make([]struct{}, 1) } func T(f []Foo) { for i := range f { f[i].Print() } }