func (cdc *Codec) collectImplementers_nolock(info *TypeInfo) {
	for _, cinfo := range cdc.concreteInfos {
		if cinfo.PtrToType.Implements(info.Type) {
			info.Implementers[cinfo.Prefix] = append(
				info.Implementers[cinfo.Prefix], cinfo)
		}
	}
}
func (cdc *Codec) collectImplementers_nolock(info *TypeInfo) {
	for _, cinfo := range cdc.concreteInfos {
		if cinfo.PtrToType.Implements(info.Type) {
			info.Implementers[cinfo.Prefix] = append(
				info.Implementers[cinfo.Prefix], cinfo)
		}
	}
}
// Find all conflicting prefixes for concrete types
// that "implement" the interface.  "Implement" in quotes because
// we only consider the pointer, for extra safety.