package pkg import "fmt" type i1 interface { String() int } type i2 interface { String() string } type i3 interface { bar() int } type i4 interface { String() int bar() int } func fn() { var v1 i1 _ = v1.(i2) // want `impossible type assertion; i1 and i2 contradict each other` _ = v1.(i3) _ = v1.(i4) _ = v1.(fmt.Stringer) // want `impossible type assertion; i1 and fmt.Stringer contradict each other` _ = v1.(interface { // want `i1 and.+String.+contradict each other` String() string }) }