func memberTypeToProtobufField()

in cmd/go-to-protobuf/protobuf/generator.go [472:546]
72 lines of code
22 McCabe index (conditional complexity)

func memberTypeToProtobufField(locator ProtobufLocator, field *protoField, t *types.Type) error {
	var err error
	switch t.Kind {
	case types.Protobuf:
		field.Type, err = locator.ProtoTypeFor(t)
	case types.Builtin:
		field.Type, err = locator.ProtoTypeFor(t)
	case types.Map:
		valueField := &protoField{}
		if err := memberTypeToProtobufField(locator, valueField, t.Elem); err != nil {
			return err
		}
		keyField := &protoField{}
		if err := memberTypeToProtobufField(locator, keyField, t.Key); err != nil {
			return err
		}
		// All other protobuf types have kind types.Protobuf, so setting types.Map
		// here would be very misleading.
		field.Type = &types.Type{
			Kind: types.Protobuf,
			Key:  keyField.Type,
			Elem: valueField.Type,
		}
		if !strings.HasPrefix(t.Name.Name, "map[") {
			field.Extras["(gogoproto.casttype)"] = strconv.Quote(locator.CastTypeName(t.Name))
		}
		if k, ok := keyField.Extras["(gogoproto.casttype)"]; ok {
			field.Extras["(gogoproto.castkey)"] = k
		}
		if v, ok := valueField.Extras["(gogoproto.casttype)"]; ok {
			field.Extras["(gogoproto.castvalue)"] = v
		}
		field.Map = true
	case types.Pointer:
		if err := memberTypeToProtobufField(locator, field, t.Elem); err != nil {
			return err
		}
		field.Nullable = true
	case types.Alias:
		if isOptionalAlias(t) {
			field.Type, err = locator.ProtoTypeFor(t)
			field.Nullable = true
		} else {
			if err := memberTypeToProtobufField(locator, field, t.Underlying); err != nil {
				log.Printf("failed to alias: %s %s: err %v", t.Name, t.Underlying.Name, err)
				return err
			}
			// If this is not an alias to a slice, cast to the alias
			if !field.Repeated {
				if field.Extras == nil {
					field.Extras = make(map[string]string)
				}
				field.Extras["(gogoproto.casttype)"] = strconv.Quote(locator.CastTypeName(t.Name))
			}
		}
	case types.Slice:
		if t.Elem.Name.Name == "byte" && len(t.Elem.Name.Package) == 0 {
			field.Type = &types.Type{Name: types.Name{Name: "bytes"}, Kind: types.Protobuf}
			return nil
		}
		if err := memberTypeToProtobufField(locator, field, t.Elem); err != nil {
			return err
		}
		field.Repeated = true
	case types.Struct:
		if len(t.Name.Name) == 0 {
			return errUnrecognizedType
		}
		field.Type, err = locator.ProtoTypeFor(t)
		field.Nullable = false
	default:
		return errUnrecognizedType
	}
	return err
}