kubernetes/staging/src/k8s.io/client-go/transport/cache_go118.go

var _ …

// assert at compile time that tlsCacheKey is comparable in a way that will never panic at runtime.
//
// Golang 1.20 introduced an exception to type constraints that allows comparable, but not
// necessarily strictly comparable type arguments to satisfy the `comparable` type constraint,
// thus allowing interfaces to fulfil the `comparable` constraint.
// However, by definition, "A comparison of two interface values with identical
// dynamic types causes a run-time panic if that type is not comparable".
//
// We want to make sure that comparing two `tlsCacheKey` elements won't cause a
// runtime panic. In order to do that, we'll force the `tlsCacheKey` to be strictly
// comparable, thus making it impossible for it to contain interfaces.
// To assert strict comparability, we'll use another definition: "Type
// parameters are comparable if they are strictly comparable".
// Below, we first construct a type parameter from the `tlsCacheKey` type so that
// we can then push this type parameter to a comparable check, thus checking these
// are strictly comparable.
//
// Original suggestion from https://github.com/golang/go/issues/56548#issuecomment-1317673963
func isCacheKeyComparable[K tlsCacheKey]() { … }

func isComparable[T comparable]() { … }