[Question]: why are there empty structs in atomic?

[mvestnik]

In atomic.go:

type noCopy struct{}

func (c *noCopy) Lock()   {}
func (c *noCopy) Unlock() {}

type atomicUint32 struct {
  _ noCopy
  v uint32
}

is this filler (_ noCopy) for semantics or does it actually prevent copying?

[semihbkgr]

noCopy implements sync.Locker so that go vet can trigger warnings when types embedding noCopy are copied.

It is primarily used to trigger go vet warnings in cases where types with the '_noCopy' field are being copied.

You can find similar use cases in the Go std package: https://github.com/golang/go/blob/48b10c9af7955bcab179b60a148a633a0a75cde7/src/sync/atomic/type.go#L191

[mvestnik]

Thank you very much, I got it.