type google.golang.org/protobuf/runtime/protoimpl.ExtensionFieldV1

2 uses

	google.golang.org/protobuf/runtime/protoimpl (current package)
		impl.go#L39: 	ExtensionFieldV1 = impl.ExtensionField

	github.com/golang/protobuf/proto
		extensions.go#L32: 	Extension = protoimpl.ExtensionFieldV1