const google.golang.org/protobuf/internal/genid.FileDescriptorProto_Extension_field_fullname

one use

	google.golang.org/protobuf/internal/genid (current package)
		descriptor_gen.go#L62: 	FileDescriptorProto_Extension_field_fullname        protoreflect.FullName = "google.protobuf.FileDescriptorProto.extension"