cmd/protoc-gen-go: add support for map fields

Generate the proper map[key]value type for map fields.
Include the protobuf_key and protobuf_val field tags.
Do not generate the map entry structs.

Fix an initialization order bug in protogen: While proto files cannot
contain circular dependencies, a single file can contain dependency
cycles. First create types for all the descriptors in a file, then add
in references (currently just field->message and field->enum) in a
second pass.

Change-Id: Ifedfa657d8dbb00413ba493adee1119b19c1b773
Reviewed-on: https://go-review.googlesource.com/135355
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>

cmd/protoc-gen-go/main.go

@@ -246,6 +246,10 @@ func enumRegistryName(enum *protogen.Enum) string {
 }
 
 func genMessage(gen *protogen.Plugin, g *protogen.GeneratedFile, f *File, message *protogen.Message) {
+	if message.Desc.IsMapEntry() {
+		return
+	}
+
 	for _, e := range message.Enums {
 		genEnum(gen, g, f, e)
 	}
@@ -263,7 +267,19 @@ func genMessage(gen *protogen.Plugin, g *protogen.GeneratedFile, f *File, messag
 		if pointer {
 			goType = "*" + goType
 		}
-		g.P(field.GoIdent, " ", goType, fmt.Sprintf(" `protobuf:%q json:%q`", fieldProtobufTag(field), fieldJSONTag(field)))
+		tags := []string{
+			fmt.Sprintf("protobuf:%q", fieldProtobufTag(field)),
+			fmt.Sprintf("json:%q", fieldJSONTag(field)),
+		}
+		if field.Desc.IsMap() {
+			key := field.MessageType.Fields[0]
+			val := field.MessageType.Fields[1]
+			tags = append(tags,
+				fmt.Sprintf("protobuf_key:%q", fieldProtobufTag(key)),
+				fmt.Sprintf("protobuf_val:%q", fieldProtobufTag(val)),
+			)
+		}
+		g.P(field.GoIdent, " ", goType, " `", strings.Join(tags, " "), "`")
 	}
 	g.P("XXX_NoUnkeyedLiteral struct{} `json:\"-\"`")
 	// TODO XXX_InternalExtensions
@@ -408,7 +424,6 @@ func genMessage(gen *protogen.Plugin, g *protogen.GeneratedFile, f *File, messag
 //
 // If it returns pointer=true, the struct field is a pointer to the type.
 func fieldGoType(g *protogen.GeneratedFile, field *protogen.Field) (goType string, pointer bool) {
-	// TODO: map types
 	pointer = true
 	switch field.Desc.Kind() {
 	case protoreflect.BoolKind:
@@ -433,6 +448,11 @@ func fieldGoType(g *protogen.GeneratedFile, field *protogen.Field) (goType strin
 		goType = "[]byte"
 		pointer = false
 	case protoreflect.MessageKind, protoreflect.GroupKind:
+		if field.Desc.IsMap() {
+			keyType, _ := fieldGoType(g, field.MessageType.Fields[0])
+			valType, _ := fieldGoType(g, field.MessageType.Fields[1])
+			return fmt.Sprintf("map[%v]%v", keyType, valType), false
+		}
 		goType = "*" + g.QualifiedGoIdent(field.MessageType.GoIdent)
 		pointer = false
 	}

cmd/protoc-gen-go/testdata/proto2/fields.pb.go

@@ -55,85 +55,88 @@ func (FieldTestMessage_Enum) EnumDescriptor() ([]byte, []int) {
 }
 
 type FieldTestMessage struct {
-	OptionalBool         *bool                             `protobuf:"varint,1,opt,name=optional_bool,json=optionalBool" json:"optional_bool,omitempty"`
-	OptionalEnum         *FieldTestMessage_Enum            `protobuf:"varint,2,opt,name=optional_enum,json=optionalEnum,enum=goproto.protoc.proto2.FieldTestMessage_Enum" json:"optional_enum,omitempty"`
-	OptionalInt32        *int32                            `protobuf:"varint,3,opt,name=optional_int32,json=optionalInt32" json:"optional_int32,omitempty"`
-	OptionalSint32       *int32                            `protobuf:"zigzag32,4,opt,name=optional_sint32,json=optionalSint32" json:"optional_sint32,omitempty"`
-	OptionalUint32       *uint32                           `protobuf:"varint,5,opt,name=optional_uint32,json=optionalUint32" json:"optional_uint32,omitempty"`
-	OptionalInt64        *int64                            `protobuf:"varint,6,opt,name=optional_int64,json=optionalInt64" json:"optional_int64,omitempty"`
-	OptionalSint64       *int64                            `protobuf:"zigzag64,7,opt,name=optional_sint64,json=optionalSint64" json:"optional_sint64,omitempty"`
-	OptionalUint64       *uint64                           `protobuf:"varint,8,opt,name=optional_uint64,json=optionalUint64" json:"optional_uint64,omitempty"`
-	OptionalSfixed32     *int32                            `protobuf:"fixed32,9,opt,name=optional_sfixed32,json=optionalSfixed32" json:"optional_sfixed32,omitempty"`
-	OptionalFixed32      *uint32                           `protobuf:"fixed32,10,opt,name=optional_fixed32,json=optionalFixed32" json:"optional_fixed32,omitempty"`
-	OptionalFloat        *float32                          `protobuf:"fixed32,11,opt,name=optional_float,json=optionalFloat" json:"optional_float,omitempty"`
-	OptionalSfixed64     *int64                            `protobuf:"fixed64,12,opt,name=optional_sfixed64,json=optionalSfixed64" json:"optional_sfixed64,omitempty"`
-	OptionalFixed64      *uint64                           `protobuf:"fixed64,13,opt,name=optional_fixed64,json=optionalFixed64" json:"optional_fixed64,omitempty"`
-	OptionalDouble       *float64                          `protobuf:"fixed64,14,opt,name=optional_double,json=optionalDouble" json:"optional_double,omitempty"`
-	OptionalString       *string                           `protobuf:"bytes,15,opt,name=optional_string,json=optionalString" json:"optional_string,omitempty"`
-	OptionalBytes        []byte                            `protobuf:"bytes,16,opt,name=optional_bytes,json=optionalBytes" json:"optional_bytes,omitempty"`
-	Optional_Message     *FieldTestMessage_Message         `protobuf:"bytes,17,opt,name=optional_Message,json=optionalMessage" json:"optional_Message,omitempty"`
-	Optionalgroup        *FieldTestMessage_OptionalGroup   `protobuf:"group,18,opt,name=OptionalGroup,json=optionalgroup" json:"optionalgroup,omitempty"`
-	RequiredBool         *bool                             `protobuf:"varint,101,req,name=required_bool,json=requiredBool" json:"required_bool,omitempty"`
-	RequiredEnum         *FieldTestMessage_Enum            `protobuf:"varint,102,req,name=required_enum,json=requiredEnum,enum=goproto.protoc.proto2.FieldTestMessage_Enum" json:"required_enum,omitempty"`
-	RequiredInt32        *int32                            `protobuf:"varint,103,req,name=required_int32,json=requiredInt32" json:"required_int32,omitempty"`
-	RequiredSint32       *int32                            `protobuf:"zigzag32,104,req,name=required_sint32,json=requiredSint32" json:"required_sint32,omitempty"`
-	RequiredUint32       *uint32                           `protobuf:"varint,105,req,name=required_uint32,json=requiredUint32" json:"required_uint32,omitempty"`
-	RequiredInt64        *int64                            `protobuf:"varint,106,req,name=required_int64,json=requiredInt64" json:"required_int64,omitempty"`
-	RequiredSint64       *int64                            `protobuf:"zigzag64,107,req,name=required_sint64,json=requiredSint64" json:"required_sint64,omitempty"`
-	RequiredUint64       *uint64                           `protobuf:"varint,108,req,name=required_uint64,json=requiredUint64" json:"required_uint64,omitempty"`
-	RequiredSfixed32     *int32                            `protobuf:"fixed32,109,req,name=required_sfixed32,json=requiredSfixed32" json:"required_sfixed32,omitempty"`
-	RequiredFixed32      *uint32                           `protobuf:"fixed32,110,req,name=required_fixed32,json=requiredFixed32" json:"required_fixed32,omitempty"`
-	RequiredFloat        *float32                          `protobuf:"fixed32,111,req,name=required_float,json=requiredFloat" json:"required_float,omitempty"`
-	RequiredSfixed64     *int64                            `protobuf:"fixed64,112,req,name=required_sfixed64,json=requiredSfixed64" json:"required_sfixed64,omitempty"`
-	RequiredFixed64      *uint64                           `protobuf:"fixed64,113,req,name=required_fixed64,json=requiredFixed64" json:"required_fixed64,omitempty"`
-	RequiredDouble       *float64                          `protobuf:"fixed64,114,req,name=required_double,json=requiredDouble" json:"required_double,omitempty"`
-	RequiredString       *string                           `protobuf:"bytes,115,req,name=required_string,json=requiredString" json:"required_string,omitempty"`
-	RequiredBytes        []byte                            `protobuf:"bytes,116,req,name=required_bytes,json=requiredBytes" json:"required_bytes,omitempty"`
-	Required_Message     *FieldTestMessage_Message         `protobuf:"bytes,117,req,name=required_Message,json=requiredMessage" json:"required_Message,omitempty"`
-	Requiredgroup        *FieldTestMessage_RequiredGroup   `protobuf:"group,118,req,name=RequiredGroup,json=requiredgroup" json:"requiredgroup,omitempty"`
-	RepeatedBool         []bool                            `protobuf:"varint,201,rep,name=repeated_bool,json=repeatedBool" json:"repeated_bool,omitempty"`
-	RepeatedEnum         []FieldTestMessage_Enum           `protobuf:"varint,202,rep,name=repeated_enum,json=repeatedEnum,enum=goproto.protoc.proto2.FieldTestMessage_Enum" json:"repeated_enum,omitempty"`
-	RepeatedInt32        []int32                           `protobuf:"varint,203,rep,name=repeated_int32,json=repeatedInt32" json:"repeated_int32,omitempty"`
-	RepeatedSint32       []int32                           `protobuf:"zigzag32,204,rep,name=repeated_sint32,json=repeatedSint32" json:"repeated_sint32,omitempty"`
-	RepeatedUint32       []uint32                          `protobuf:"varint,205,rep,name=repeated_uint32,json=repeatedUint32" json:"repeated_uint32,omitempty"`
-	RepeatedInt64        []int64                           `protobuf:"varint,206,rep,name=repeated_int64,json=repeatedInt64" json:"repeated_int64,omitempty"`
-	RepeatedSint64       []int64                           `protobuf:"zigzag64,207,rep,name=repeated_sint64,json=repeatedSint64" json:"repeated_sint64,omitempty"`
-	RepeatedUint64       []uint64                          `protobuf:"varint,208,rep,name=repeated_uint64,json=repeatedUint64" json:"repeated_uint64,omitempty"`
-	RepeatedSfixed32     []int32                           `protobuf:"fixed32,209,rep,name=repeated_sfixed32,json=repeatedSfixed32" json:"repeated_sfixed32,omitempty"`
-	RepeatedFixed32      []uint32                          `protobuf:"fixed32,210,rep,name=repeated_fixed32,json=repeatedFixed32" json:"repeated_fixed32,omitempty"`
-	RepeatedFloat        []float32                         `protobuf:"fixed32,211,rep,name=repeated_float,json=repeatedFloat" json:"repeated_float,omitempty"`
-	RepeatedSfixed64     []int64                           `protobuf:"fixed64,212,rep,name=repeated_sfixed64,json=repeatedSfixed64" json:"repeated_sfixed64,omitempty"`
-	RepeatedFixed64      []uint64                          `protobuf:"fixed64,213,rep,name=repeated_fixed64,json=repeatedFixed64" json:"repeated_fixed64,omitempty"`
-	RepeatedDouble       []float64                         `protobuf:"fixed64,214,rep,name=repeated_double,json=repeatedDouble" json:"repeated_double,omitempty"`
-	RepeatedString       []string                          `protobuf:"bytes,215,rep,name=repeated_string,json=repeatedString" json:"repeated_string,omitempty"`
-	RepeatedBytes        [][]byte                          `protobuf:"bytes,216,rep,name=repeated_bytes,json=repeatedBytes" json:"repeated_bytes,omitempty"`
-	Repeated_Message     []*FieldTestMessage_Message       `protobuf:"bytes,217,rep,name=repeated_Message,json=repeatedMessage" json:"repeated_Message,omitempty"`
-	Repeatedgroup        []*FieldTestMessage_RepeatedGroup `protobuf:"group,218,rep,name=RepeatedGroup,json=repeatedgroup" json:"repeatedgroup,omitempty"`
-	DefaultBool          *bool                             `protobuf:"varint,301,opt,name=default_bool,json=defaultBool,def=1" json:"default_bool,omitempty"`
-	DefaultEnum          *FieldTestMessage_Enum            `protobuf:"varint,302,opt,name=default_enum,json=defaultEnum,enum=goproto.protoc.proto2.FieldTestMessage_Enum,def=1" json:"default_enum,omitempty"`
-	DefaultInt32         *int32                            `protobuf:"varint,303,opt,name=default_int32,json=defaultInt32,def=1" json:"default_int32,omitempty"`
-	DefaultSint32        *int32                            `protobuf:"zigzag32,304,opt,name=default_sint32,json=defaultSint32,def=1" json:"default_sint32,omitempty"`
-	DefaultUint32        *uint32                           `protobuf:"varint,305,opt,name=default_uint32,json=defaultUint32,def=1" json:"default_uint32,omitempty"`
-	DefaultInt64         *int64                            `protobuf:"varint,306,opt,name=default_int64,json=defaultInt64,def=1" json:"default_int64,omitempty"`
-	DefaultSint64        *int64                            `protobuf:"zigzag64,307,opt,name=default_sint64,json=defaultSint64,def=1" json:"default_sint64,omitempty"`
-	DefaultUint64        *uint64                           `protobuf:"varint,308,opt,name=default_uint64,json=defaultUint64,def=1" json:"default_uint64,omitempty"`
-	DefaultSfixed32      *int32                            `protobuf:"fixed32,309,opt,name=default_sfixed32,json=defaultSfixed32,def=1" json:"default_sfixed32,omitempty"`
-	DefaultFixed32       *uint32                           `protobuf:"fixed32,310,opt,name=default_fixed32,json=defaultFixed32,def=1" json:"default_fixed32,omitempty"`
-	DefaultFloat         *float32                          `protobuf:"fixed32,311,opt,name=default_float,json=defaultFloat,def=1.5" json:"default_float,omitempty"`
-	DefaultSfixed64      *int64                            `protobuf:"fixed64,312,opt,name=default_sfixed64,json=defaultSfixed64,def=1" json:"default_sfixed64,omitempty"`
-	DefaultFixed64       *uint64                           `protobuf:"fixed64,313,opt,name=default_fixed64,json=defaultFixed64,def=1" json:"default_fixed64,omitempty"`
-	DefaultDouble        *float64                          `protobuf:"fixed64,314,opt,name=default_double,json=defaultDouble,def=1.5" json:"default_double,omitempty"`
-	DefaultString        *string                           `protobuf:"bytes,315,opt,name=default_string,json=defaultString,def=x,y" json:"default_string,omitempty"`
-	DefaultBytes         []byte                            `protobuf:"bytes,316,opt,name=default_bytes,json=defaultBytes,def=x,y" json:"default_bytes,omitempty"`
-	DefaultFloatNeginf   *float32                          `protobuf:"fixed32,400,opt,name=default_float_neginf,json=defaultFloatNeginf,def=-inf" json:"default_float_neginf,omitempty"`
-	DefaultFloatPosinf   *float32                          `protobuf:"fixed32,401,opt,name=default_float_posinf,json=defaultFloatPosinf,def=inf" json:"default_float_posinf,omitempty"`
-	DefaultFloatNan      *float32                          `protobuf:"fixed32,402,opt,name=default_float_nan,json=defaultFloatNan,def=nan" json:"default_float_nan,omitempty"`
-	DefaultDoubleNeginf  *float64                          `protobuf:"fixed64,403,opt,name=default_double_neginf,json=defaultDoubleNeginf,def=-inf" json:"default_double_neginf,omitempty"`
-	DefaultDoublePosinf  *float64                          `protobuf:"fixed64,404,opt,name=default_double_posinf,json=defaultDoublePosinf,def=inf" json:"default_double_posinf,omitempty"`
-	DefaultDoubleNan     *float64                          `protobuf:"fixed64,405,opt,name=default_double_nan,json=defaultDoubleNan,def=nan" json:"default_double_nan,omitempty"`
-	XXX_NoUnkeyedLiteral struct{}                          `json:"-"`
-	XXX_unrecognized     []byte                            `json:"-"`
-	XXX_sizecache        int32                             `json:"-"`
+	OptionalBool         *bool                                `protobuf:"varint,1,opt,name=optional_bool,json=optionalBool" json:"optional_bool,omitempty"`
+	OptionalEnum         *FieldTestMessage_Enum               `protobuf:"varint,2,opt,name=optional_enum,json=optionalEnum,enum=goproto.protoc.proto2.FieldTestMessage_Enum" json:"optional_enum,omitempty"`
+	OptionalInt32        *int32                               `protobuf:"varint,3,opt,name=optional_int32,json=optionalInt32" json:"optional_int32,omitempty"`
+	OptionalSint32       *int32                               `protobuf:"zigzag32,4,opt,name=optional_sint32,json=optionalSint32" json:"optional_sint32,omitempty"`
+	OptionalUint32       *uint32                              `protobuf:"varint,5,opt,name=optional_uint32,json=optionalUint32" json:"optional_uint32,omitempty"`
+	OptionalInt64        *int64                               `protobuf:"varint,6,opt,name=optional_int64,json=optionalInt64" json:"optional_int64,omitempty"`
+	OptionalSint64       *int64                               `protobuf:"zigzag64,7,opt,name=optional_sint64,json=optionalSint64" json:"optional_sint64,omitempty"`
+	OptionalUint64       *uint64                              `protobuf:"varint,8,opt,name=optional_uint64,json=optionalUint64" json:"optional_uint64,omitempty"`
+	OptionalSfixed32     *int32                               `protobuf:"fixed32,9,opt,name=optional_sfixed32,json=optionalSfixed32" json:"optional_sfixed32,omitempty"`
+	OptionalFixed32      *uint32                              `protobuf:"fixed32,10,opt,name=optional_fixed32,json=optionalFixed32" json:"optional_fixed32,omitempty"`
+	OptionalFloat        *float32                             `protobuf:"fixed32,11,opt,name=optional_float,json=optionalFloat" json:"optional_float,omitempty"`
+	OptionalSfixed64     *int64                               `protobuf:"fixed64,12,opt,name=optional_sfixed64,json=optionalSfixed64" json:"optional_sfixed64,omitempty"`
+	OptionalFixed64      *uint64                              `protobuf:"fixed64,13,opt,name=optional_fixed64,json=optionalFixed64" json:"optional_fixed64,omitempty"`
+	OptionalDouble       *float64                             `protobuf:"fixed64,14,opt,name=optional_double,json=optionalDouble" json:"optional_double,omitempty"`
+	OptionalString       *string                              `protobuf:"bytes,15,opt,name=optional_string,json=optionalString" json:"optional_string,omitempty"`
+	OptionalBytes        []byte                               `protobuf:"bytes,16,opt,name=optional_bytes,json=optionalBytes" json:"optional_bytes,omitempty"`
+	Optional_Message     *FieldTestMessage_Message            `protobuf:"bytes,17,opt,name=optional_Message,json=optionalMessage" json:"optional_Message,omitempty"`
+	Optionalgroup        *FieldTestMessage_OptionalGroup      `protobuf:"group,18,opt,name=OptionalGroup,json=optionalgroup" json:"optionalgroup,omitempty"`
+	RequiredBool         *bool                                `protobuf:"varint,101,req,name=required_bool,json=requiredBool" json:"required_bool,omitempty"`
+	RequiredEnum         *FieldTestMessage_Enum               `protobuf:"varint,102,req,name=required_enum,json=requiredEnum,enum=goproto.protoc.proto2.FieldTestMessage_Enum" json:"required_enum,omitempty"`
+	RequiredInt32        *int32                               `protobuf:"varint,103,req,name=required_int32,json=requiredInt32" json:"required_int32,omitempty"`
+	RequiredSint32       *int32                               `protobuf:"zigzag32,104,req,name=required_sint32,json=requiredSint32" json:"required_sint32,omitempty"`
+	RequiredUint32       *uint32                              `protobuf:"varint,105,req,name=required_uint32,json=requiredUint32" json:"required_uint32,omitempty"`
+	RequiredInt64        *int64                               `protobuf:"varint,106,req,name=required_int64,json=requiredInt64" json:"required_int64,omitempty"`
+	RequiredSint64       *int64                               `protobuf:"zigzag64,107,req,name=required_sint64,json=requiredSint64" json:"required_sint64,omitempty"`
+	RequiredUint64       *uint64                              `protobuf:"varint,108,req,name=required_uint64,json=requiredUint64" json:"required_uint64,omitempty"`
+	RequiredSfixed32     *int32                               `protobuf:"fixed32,109,req,name=required_sfixed32,json=requiredSfixed32" json:"required_sfixed32,omitempty"`
+	RequiredFixed32      *uint32                              `protobuf:"fixed32,110,req,name=required_fixed32,json=requiredFixed32" json:"required_fixed32,omitempty"`
+	RequiredFloat        *float32                             `protobuf:"fixed32,111,req,name=required_float,json=requiredFloat" json:"required_float,omitempty"`
+	RequiredSfixed64     *int64                               `protobuf:"fixed64,112,req,name=required_sfixed64,json=requiredSfixed64" json:"required_sfixed64,omitempty"`
+	RequiredFixed64      *uint64                              `protobuf:"fixed64,113,req,name=required_fixed64,json=requiredFixed64" json:"required_fixed64,omitempty"`
+	RequiredDouble       *float64                             `protobuf:"fixed64,114,req,name=required_double,json=requiredDouble" json:"required_double,omitempty"`
+	RequiredString       *string                              `protobuf:"bytes,115,req,name=required_string,json=requiredString" json:"required_string,omitempty"`
+	RequiredBytes        []byte                               `protobuf:"bytes,116,req,name=required_bytes,json=requiredBytes" json:"required_bytes,omitempty"`
+	Required_Message     *FieldTestMessage_Message            `protobuf:"bytes,117,req,name=required_Message,json=requiredMessage" json:"required_Message,omitempty"`
+	Requiredgroup        *FieldTestMessage_RequiredGroup      `protobuf:"group,118,req,name=RequiredGroup,json=requiredgroup" json:"requiredgroup,omitempty"`
+	RepeatedBool         []bool                               `protobuf:"varint,201,rep,name=repeated_bool,json=repeatedBool" json:"repeated_bool,omitempty"`
+	RepeatedEnum         []FieldTestMessage_Enum              `protobuf:"varint,202,rep,name=repeated_enum,json=repeatedEnum,enum=goproto.protoc.proto2.FieldTestMessage_Enum" json:"repeated_enum,omitempty"`
+	RepeatedInt32        []int32                              `protobuf:"varint,203,rep,name=repeated_int32,json=repeatedInt32" json:"repeated_int32,omitempty"`
+	RepeatedSint32       []int32                              `protobuf:"zigzag32,204,rep,name=repeated_sint32,json=repeatedSint32" json:"repeated_sint32,omitempty"`
+	RepeatedUint32       []uint32                             `protobuf:"varint,205,rep,name=repeated_uint32,json=repeatedUint32" json:"repeated_uint32,omitempty"`
+	RepeatedInt64        []int64                              `protobuf:"varint,206,rep,name=repeated_int64,json=repeatedInt64" json:"repeated_int64,omitempty"`
+	RepeatedSint64       []int64                              `protobuf:"zigzag64,207,rep,name=repeated_sint64,json=repeatedSint64" json:"repeated_sint64,omitempty"`
+	RepeatedUint64       []uint64                             `protobuf:"varint,208,rep,name=repeated_uint64,json=repeatedUint64" json:"repeated_uint64,omitempty"`
+	RepeatedSfixed32     []int32                              `protobuf:"fixed32,209,rep,name=repeated_sfixed32,json=repeatedSfixed32" json:"repeated_sfixed32,omitempty"`
+	RepeatedFixed32      []uint32                             `protobuf:"fixed32,210,rep,name=repeated_fixed32,json=repeatedFixed32" json:"repeated_fixed32,omitempty"`
+	RepeatedFloat        []float32                            `protobuf:"fixed32,211,rep,name=repeated_float,json=repeatedFloat" json:"repeated_float,omitempty"`
+	RepeatedSfixed64     []int64                              `protobuf:"fixed64,212,rep,name=repeated_sfixed64,json=repeatedSfixed64" json:"repeated_sfixed64,omitempty"`
+	RepeatedFixed64      []uint64                             `protobuf:"fixed64,213,rep,name=repeated_fixed64,json=repeatedFixed64" json:"repeated_fixed64,omitempty"`
+	RepeatedDouble       []float64                            `protobuf:"fixed64,214,rep,name=repeated_double,json=repeatedDouble" json:"repeated_double,omitempty"`
+	RepeatedString       []string                             `protobuf:"bytes,215,rep,name=repeated_string,json=repeatedString" json:"repeated_string,omitempty"`
+	RepeatedBytes        [][]byte                             `protobuf:"bytes,216,rep,name=repeated_bytes,json=repeatedBytes" json:"repeated_bytes,omitempty"`
+	Repeated_Message     []*FieldTestMessage_Message          `protobuf:"bytes,217,rep,name=repeated_Message,json=repeatedMessage" json:"repeated_Message,omitempty"`
+	Repeatedgroup        []*FieldTestMessage_RepeatedGroup    `protobuf:"group,218,rep,name=RepeatedGroup,json=repeatedgroup" json:"repeatedgroup,omitempty"`
+	DefaultBool          *bool                                `protobuf:"varint,301,opt,name=default_bool,json=defaultBool,def=1" json:"default_bool,omitempty"`
+	DefaultEnum          *FieldTestMessage_Enum               `protobuf:"varint,302,opt,name=default_enum,json=defaultEnum,enum=goproto.protoc.proto2.FieldTestMessage_Enum,def=1" json:"default_enum,omitempty"`
+	DefaultInt32         *int32                               `protobuf:"varint,303,opt,name=default_int32,json=defaultInt32,def=1" json:"default_int32,omitempty"`
+	DefaultSint32        *int32                               `protobuf:"zigzag32,304,opt,name=default_sint32,json=defaultSint32,def=1" json:"default_sint32,omitempty"`
+	DefaultUint32        *uint32                              `protobuf:"varint,305,opt,name=default_uint32,json=defaultUint32,def=1" json:"default_uint32,omitempty"`
+	DefaultInt64         *int64                               `protobuf:"varint,306,opt,name=default_int64,json=defaultInt64,def=1" json:"default_int64,omitempty"`
+	DefaultSint64        *int64                               `protobuf:"zigzag64,307,opt,name=default_sint64,json=defaultSint64,def=1" json:"default_sint64,omitempty"`
+	DefaultUint64        *uint64                              `protobuf:"varint,308,opt,name=default_uint64,json=defaultUint64,def=1" json:"default_uint64,omitempty"`
+	DefaultSfixed32      *int32                               `protobuf:"fixed32,309,opt,name=default_sfixed32,json=defaultSfixed32,def=1" json:"default_sfixed32,omitempty"`
+	DefaultFixed32       *uint32                              `protobuf:"fixed32,310,opt,name=default_fixed32,json=defaultFixed32,def=1" json:"default_fixed32,omitempty"`
+	DefaultFloat         *float32                             `protobuf:"fixed32,311,opt,name=default_float,json=defaultFloat,def=1.5" json:"default_float,omitempty"`
+	DefaultSfixed64      *int64                               `protobuf:"fixed64,312,opt,name=default_sfixed64,json=defaultSfixed64,def=1" json:"default_sfixed64,omitempty"`
+	DefaultFixed64       *uint64                              `protobuf:"fixed64,313,opt,name=default_fixed64,json=defaultFixed64,def=1" json:"default_fixed64,omitempty"`
+	DefaultDouble        *float64                             `protobuf:"fixed64,314,opt,name=default_double,json=defaultDouble,def=1.5" json:"default_double,omitempty"`
+	DefaultString        *string                              `protobuf:"bytes,315,opt,name=default_string,json=defaultString,def=x,y" json:"default_string,omitempty"`
+	DefaultBytes         []byte                               `protobuf:"bytes,316,opt,name=default_bytes,json=defaultBytes,def=x,y" json:"default_bytes,omitempty"`
+	DefaultFloatNeginf   *float32                             `protobuf:"fixed32,400,opt,name=default_float_neginf,json=defaultFloatNeginf,def=-inf" json:"default_float_neginf,omitempty"`
+	DefaultFloatPosinf   *float32                             `protobuf:"fixed32,401,opt,name=default_float_posinf,json=defaultFloatPosinf,def=inf" json:"default_float_posinf,omitempty"`
+	DefaultFloatNan      *float32                             `protobuf:"fixed32,402,opt,name=default_float_nan,json=defaultFloatNan,def=nan" json:"default_float_nan,omitempty"`
+	DefaultDoubleNeginf  *float64                             `protobuf:"fixed64,403,opt,name=default_double_neginf,json=defaultDoubleNeginf,def=-inf" json:"default_double_neginf,omitempty"`
+	DefaultDoublePosinf  *float64                             `protobuf:"fixed64,404,opt,name=default_double_posinf,json=defaultDoublePosinf,def=inf" json:"default_double_posinf,omitempty"`
+	DefaultDoubleNan     *float64                             `protobuf:"fixed64,405,opt,name=default_double_nan,json=defaultDoubleNan,def=nan" json:"default_double_nan,omitempty"`
+	MapInt32Int64        map[int32]int64                      `protobuf:"bytes,500,rep,name=map_int32_int64,json=mapInt32Int64" json:"map_int32_int64,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"varint,2,opt,name=value"`
+	MapStringMessage     map[string]*FieldTestMessage_Message `protobuf:"bytes,501,rep,name=map_string_message,json=mapStringMessage" json:"map_string_message,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
+	MapFixed64Enum       map[uint64]FieldTestMessage_Enum     `protobuf:"bytes,502,rep,name=map_fixed64_enum,json=mapFixed64Enum" json:"map_fixed64_enum,omitempty" protobuf_key:"fixed64,1,opt,name=key" protobuf_val:"varint,2,opt,name=value,enum=goproto.protoc.proto2.FieldTestMessage_Enum"`
+	XXX_NoUnkeyedLiteral struct{}                             `json:"-"`
+	XXX_unrecognized     []byte                               `json:"-"`
+	XXX_sizecache        int32                                `json:"-"`
 }
 
 func (m *FieldTestMessage) Reset()         { *m = FieldTestMessage{} }
@@ -716,6 +719,27 @@ func (m *FieldTestMessage) GetDefaultDoubleNan() float64 {
 	return Default_FieldTestMessage_DefaultDoubleNan
 }
 
+func (m *FieldTestMessage) GetMapInt32Int64() map[int32]int64 {
+	if m != nil {
+		return m.MapInt32Int64
+	}
+	return nil
+}
+
+func (m *FieldTestMessage) GetMapStringMessage() map[string]*FieldTestMessage_Message {
+	if m != nil {
+		return m.MapStringMessage
+	}
+	return nil
+}
+
+func (m *FieldTestMessage) GetMapFixed64Enum() map[uint64]FieldTestMessage_Enum {
+	if m != nil {
+		return m.MapFixed64Enum
+	}
+	return nil
+}
+
 type FieldTestMessage_OptionalGroup struct {
 	OptionalGroup        *string  `protobuf:"bytes,19,opt,name=optional_group,json=optionalGroup" json:"optional_group,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
@@ -840,7 +864,7 @@ func (m *FieldTestMessage_Message) Reset()         { *m = FieldTestMessage_Messa
 func (m *FieldTestMessage_Message) String() string { return proto.CompactTextString(m) }
 func (*FieldTestMessage_Message) ProtoMessage()    {}
 func (*FieldTestMessage_Message) Descriptor() ([]byte, []int) {
-	return fileDescriptor_fd8a9d72b841fd68, []int{0, 3}
+	return fileDescriptor_fd8a9d72b841fd68, []int{0, 6}
 }
 func (m *FieldTestMessage_Message) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_FieldTestMessage_Message.Unmarshal(m, b)
@@ -867,89 +891,99 @@ func init() {
 func init() { proto.RegisterFile("proto2/fields.proto", fileDescriptor_fd8a9d72b841fd68) }
 
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+	0xcb, 0x51, 0x43, 0xd7, 0x94, 0x71, 0x7a, 0x9a, 0xe8, 0xd8, 0xb6, 0xd2, 0x12, 0xee, 0xf8, 0x73,
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+	0x58, 0xd0, 0x16, 0x04, 0xf7, 0xb0, 0x0f, 0x03, 0xb6, 0xc8, 0x1d, 0xbf, 0x51, 0xb6, 0x0f, 0x83,
+	0xaa, 0x7d, 0x18, 0xb0, 0x3a, 0x77, 0xfc, 0xd9, 0x92, 0x7d, 0x69, 0xfd, 0x9d, 0x6c, 0x7a, 0x6b,
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+	0x85, 0x3b, 0xfe, 0x91, 0xd6, 0xfa, 0x7e, 0xf7, 0xa5, 0xfc, 0x5b, 0x2c, 0x4a, 0x51, 0x71, 0xb3,
+	0xd8, 0xf0, 0xbd, 0x71, 0x36, 0x1d, 0x31, 0xca, 0x1d, 0x9f, 0xb4, 0x2e, 0xec, 0xb7, 0xf0, 0x35,
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+	0x91, 0x4b, 0xb8, 0x0b, 0xc8, 0xa9, 0xa0, 0x42, 0x4e, 0x8b, 0x04, 0x72, 0x5d, 0xee, 0x1e, 0x1c,
+	0x39, 0x55, 0x42, 0x21, 0xa7, 0x4b, 0x22, 0x21, 0x3d, 0xee, 0x02, 0x72, 0x2a, 0xaa, 0x91, 0xd3,
+	0x32, 0x89, 0xdc, 0x73, 0xdc, 0x05, 0xe4, 0x54, 0xb8, 0x40, 0x4e, 0x0b, 0x25, 0x72, 0x7d, 0xee,
+	0x02, 0x72, 0x2a, 0x5c, 0x20, 0x67, 0x1a, 0x87, 0x01, 0x7b, 0x9e, 0xbb, 0x80, 0x9c, 0x61, 0x8c,
+	0x3b, 0xc9, 0x32, 0x0e, 0x03, 0x76, 0x9b, 0xbb, 0x80, 0x9c, 0x69, 0x5c, 0x12, 0x4a, 0xe4, 0x06,
+	0xdc, 0x05, 0xe4, 0x4c, 0x63, 0x44, 0xae, 0xa8, 0xa8, 0x30, 0x1a, 0x72, 0x17, 0x90, 0xd3, 0x35,
+	0x0d, 0xe4, 0xb4, 0x58, 0x69, 0x53, 0xee, 0x02, 0x72, 0x2a, 0x6e, 0x20, 0x57, 0x48, 0x05, 0x72,
+	0x19, 0x77, 0x01, 0x39, 0x2d, 0x54, 0xc8, 0x95, 0xec, 0xc3, 0x80, 0x8d, 0xb8, 0x0b, 0xc8, 0xd9,
+	0xf6, 0x88, 0x9c, 0x6d, 0x1f, 0x06, 0xec, 0x0e, 0x77, 0x01, 0x39, 0xcb, 0xbe, 0xb4, 0x7e, 0x89,
+	0xdc, 0x98, 0xbb, 0x80, 0x9c, 0x0a, 0x17, 0xc8, 0x15, 0x0d, 0x20, 0x72, 0x13, 0xee, 0x02, 0x72,
+	0xda, 0x5e, 0x23, 0x57, 0x6c, 0x49, 0x81, 0x5c, 0xce, 0x5d, 0x40, 0x4e, 0xef, 0x49, 0x85, 0x9c,
+	0x96, 0x29, 0xe4, 0xa6, 0xdc, 0x3d, 0x14, 0x72, 0xaa, 0x90, 0x81, 0x9c, 0x0a, 0x21, 0x72, 0x77,
+	0xb9, 0x7b, 0x10, 0xe4, 0x22, 0x99, 0x2c, 0x91, 0xb3, 0x6a, 0xd1, 0xfb, 0xa0, 0xf8, 0x28, 0x89,
+	0x73, 0x85, 0xdc, 0xe7, 0x0e, 0xf7, 0x90, 0x39, 0x8c, 0x0a, 0xe6, 0x22, 0x43, 0x25, 0x98, 0xfb,
+	0x02, 0x54, 0x87, 0x80, 0x0e, 0x6b, 0x08, 0xe8, 0x1e, 0x80, 0xc9, 0xca, 0x9a, 0xc8, 0xc8, 0x97,
+	0x50, 0x54, 0x50, 0x87, 0x61, 0xa4, 0xce, 0x87, 0x9f, 0x4a, 0xea, 0x24, 0x75, 0x5f, 0x81, 0x50,
+	0x60, 0x87, 0x71, 0x89, 0x9d, 0xa9, 0x94, 0xd8, 0x7d, 0x0d, 0xca, 0x7a, 0xa1, 0x94, 0xdc, 0x95,
+	0xbc, 0xc3, 0x80, 0x7d, 0x03, 0x42, 0xcf, 0xf2, 0x0e, 0x83, 0x8a, 0x77, 0x18, 0xb0, 0x6f, 0x41,
+	0x48, 0x6d, 0xef, 0x92, 0x52, 0x92, 0xf7, 0x1d, 0x28, 0x6b, 0xb6, 0x77, 0x18, 0xd0, 0xb3, 0xb0,
+	0xf7, 0x55, 0x4d, 0x85, 0xd3, 0xf7, 0xa0, 0x15, 0xec, 0xc9, 0xaa, 0x8a, 0xbd, 0x07, 0x89, 0x8e,
+	0x69, 0xf6, 0x7e, 0x00, 0xb1, 0x80, 0x0f, 0x2f, 0x28, 0xf8, 0xcc, 0x55, 0x21, 0x7c, 0x3f, 0x82,
+	0xd2, 0x2d, 0x56, 0x85, 0xf4, 0x55, 0x3b, 0x08, 0x03, 0xf6, 0x13, 0x48, 0x1b, 0xe5, 0x0e, 0xc2,
+	0xa0, 0xda, 0x41, 0x18, 0xb0, 0x9f, 0x41, 0x3c, 0x5b, 0xea, 0xa0, 0x34, 0x05, 0xc9, 0xdf, 0x2f,
+	0x20, 0x75, 0x8a, 0x29, 0x48, 0x00, 0xad, 0xc9, 0x22, 0x80, 0xbf, 0x82, 0x72, 0xc1, 0x98, 0x2c,
+	0x12, 0x68, 0xae, 0x0a, 0x09, 0xfc, 0x0d, 0x84, 0x8b, 0xc5, 0xaa, 0x10, 0xc1, 0x9b, 0x46, 0x9f,
+	0x0a, 0xc1, 0xdf, 0x41, 0x79, 0x38, 0x06, 0xb1, 0x92, 0x62, 0xf0, 0xd9, 0x02, 0x00, 0x64, 0xf0,
+	0x0f, 0xa8, 0x7c, 0x20, 0x08, 0x31, 0x5b, 0x43, 0x68, 0x14, 0xa3, 0x3e, 0x59, 0xec, 0x24, 0xdd,
+	0x78, 0x3a, 0xc8, 0x91, 0xc1, 0xd7, 0xe1, 0x29, 0x72, 0xbe, 0x5d, 0xcb, 0xc7, 0xd3, 0x24, 0x3a,
+	0x22, 0x2f, 0x09, 0x10, 0xaf, 0x17, 0x4a, 0xc1, 0xe1, 0x1b, 0x87, 0x78, 0xde, 0x6c, 0x7b, 0xd7,
+	0xae, 0x6e, 0xea, 0xb2, 0x82, 0xc5, 0x53, 0xa4, 0xae, 0xca, 0x22, 0x37, 0x6f, 0x42, 0xdd, 0x99,
+	0xb6, 0x73, 0x2e, 0x52, 0x7e, 0x08, 0xe3, 0x69, 0xb2, 0xa4, 0x84, 0x92, 0xc5, 0xb7, 0x40, 0xb9,
+	0x02, 0x4a, 0x55, 0x42, 0xd2, 0x68, 0x48, 0x25, 0x8c, 0x6f, 0x83, 0xb4, 0x6e, 0x4a, 0xaf, 0xab,
+	0xf3, 0xd2, 0xb4, 0x0f, 0x03, 0xf6, 0x0e, 0x28, 0xbd, 0x92, 0xbd, 0x38, 0x0a, 0x2c, 0xfb, 0x30,
+	0x60, 0xef, 0x82, 0x92, 0x96, 0xed, 0x6d, 0xa9, 0xe4, 0xf1, 0x3d, 0x90, 0xd6, 0xca, 0xf6, 0x61,
+	0x40, 0xd7, 0x48, 0x43, 0x57, 0x55, 0x8c, 0xbd, 0x0f, 0xe2, 0x65, 0x10, 0x2f, 0xab, 0xba, 0x0a,
+	0xc9, 0x33, 0x44, 0x85, 0x34, 0x91, 0x1f, 0x80, 0x7a, 0x0e, 0xd4, 0xca, 0x74, 0x4b, 0x9f, 0x9d,
+	0x7a, 0x69, 0x88, 0xe4, 0x87, 0x20, 0x75, 0xdb, 0xde, 0xb9, 0xe6, 0x05, 0xbd, 0x38, 0xc4, 0xb2,
+	0xd2, 0x46, 0x18, 0xb0, 0x8f, 0x40, 0xdd, 0xa8, 0xb6, 0x21, 0x8e, 0x70, 0xbb, 0x8d, 0x30, 0x60,
+	0x1f, 0x83, 0x7a, 0xb6, 0xd2, 0x86, 0x10, 0xeb, 0x69, 0x48, 0x2e, 0x3f, 0x01, 0xad, 0x83, 0x7d,
+	0xa8, 0x16, 0x25, 0x9b, 0x86, 0x58, 0xa2, 0xf9, 0x29, 0x88, 0x17, 0xda, 0xde, 0xbd, 0xb3, 0xbb,
+	0xc5, 0x9c, 0x11, 0x4f, 0x63, 0x81, 0x48, 0xe7, 0x67, 0xa0, 0x5d, 0x44, 0xad, 0x5a, 0x20, 0x12,
+	0x7a, 0x91, 0x1c, 0xb5, 0x66, 0xb1, 0x9d, 0x26, 0xbd, 0x7e, 0xda, 0x65, 0x2f, 0x7a, 0x62, 0x24,
+	0xb5, 0xb5, 0x7e, 0xda, 0x8d, 0xa8, 0x39, 0x93, 0xab, 0x42, 0x40, 0xc3, 0x72, 0xe2, 0x28, 0x9b,
+	0x40, 0xe2, 0x4b, 0x98, 0xe8, 0x55, 0xf2, 0x9e, 0x14, 0xd7, 0xe9, 0x43, 0x64, 0xa5, 0x64, 0x18,
+	0xa7, 0xec, 0x65, 0x99, 0x94, 0xc6, 0xa9, 0x1e, 0x2a, 0x9a, 0xc5, 0x29, 0xbd, 0x4c, 0x8e, 0xd9,
+	0x73, 0x52, 0x3d, 0xbe, 0xe2, 0x89, 0x71, 0x61, 0x8f, 0xab, 0xd6, 0xbc, 0x64, 0x93, 0x97, 0x2a,
+	0xa9, 0xb2, 0xcb, 0x57, 0x31, 0xd5, 0xab, 0x66, 0xca, 0x36, 0x5b, 0x84, 0x96, 0x4d, 0xe3, 0x94,
+	0xbd, 0x26, 0xd3, 0xa0, 0xcf, 0x86, 0x6d, 0x18, 0xa7, 0x74, 0x87, 0x2c, 0x0f, 0xe3, 0x11, 0xd2,
+	0x2a, 0xa1, 0xf9, 0xdb, 0x13, 0x37, 0xbb, 0xf6, 0xbe, 0x6f, 0x76, 0xf1, 0x48, 0x40, 0x2d, 0xd0,
+	0xda, 0x4c, 0xf3, 0xf1, 0x6e, 0x54, 0x1f, 0x9a, 0x31, 0x3a, 0x20, 0x14, 0x4c, 0x70, 0x13, 0x6c,
+	0x0f, 0xe5, 0x4d, 0xf5, 0x1f, 0xf4, 0x79, 0xf8, 0x00, 0x3e, 0xb8, 0x57, 0x64, 0x00, 0xad, 0x1a,
+	0xc3, 0x52, 0x98, 0x76, 0x09, 0xc4, 0xd4, 0x66, 0xc6, 0xfb, 0xdb, 0xbf, 0xe8, 0x75, 0xe5, 0x00,
+	0x5e, 0x72, 0xcb, 0xc3, 0x7d, 0x0d, 0x9d, 0x96, 0x86, 0x56, 0xf0, 0x78, 0x48, 0xea, 0xd6, 0x5b,
+	0x88, 0xf5, 0x5a, 0x85, 0x77, 0xf7, 0x55, 0xf1, 0xfa, 0xa5, 0xdf, 0x4e, 0x84, 0x0c, 0xf2, 0xac,
+	0x47, 0x29, 0xeb, 0xd9, 0x10, 0xf3, 0x5e, 0x10, 0xcf, 0x90, 0xfa, 0x11, 0x0b, 0xf3, 0x2e, 0x42,
+	0x9e, 0x71, 0xf7, 0xb7, 0x4e, 0x34, 0xcc, 0xfb, 0x13, 0x8f, 0x3e, 0x7d, 0x2c, 0x60, 0xe2, 0x23,
+	0x84, 0x56, 0x7f, 0x23, 0xda, 0x20, 0xde, 0xed, 0x64, 0x57, 0xfc, 0x37, 0x62, 0x26, 0x82, 0x8f,
+	0xf4, 0x28, 0x99, 0xb9, 0x1b, 0x0f, 0xa6, 0x89, 0xf8, 0xe7, 0x83, 0x17, 0xe1, 0x97, 0xb6, 0x7b,
+	0xc9, 0x39, 0x9e, 0x93, 0x63, 0x7b, 0x4e, 0xdf, 0x2c, 0xb2, 0x80, 0x45, 0x36, 0xcd, 0x22, 0x87,
+	0x38, 0x32, 0x0d, 0xd7, 0x8c, 0xac, 0xee, 0xf1, 0x3b, 0x98, 0x9e, 0xb3, 0xe8, 0xb9, 0x61, 0x7a,
+	0x1e, 0xf4, 0x69, 0xd2, 0x30, 0x5c, 0x20, 0x73, 0xf2, 0xd2, 0x89, 0xff, 0x93, 0x9a, 0x38, 0xd1,
+	0xe6, 0x49, 0xed, 0xc6, 0x66, 0x74, 0xad, 0xf1, 0x3f, 0x3a, 0x47, 0xe0, 0xbc, 0x6b, 0x38, 0x1b,
+	0x57, 0x6e, 0x5c, 0xee, 0x65, 0x59, 0x6f, 0x90, 0x34, 0x7b, 0xd9, 0x20, 0x4e, 0x7b, 0xcd, 0x6c,
+	0xdc, 0x5b, 0x17, 0x16, 0xeb, 0x3b, 0xc3, 0x0e, 0x7e, 0xda, 0x59, 0xeb, 0x25, 0xe9, 0x5a, 0x2f,
+	0x5b, 0xcf, 0x93, 0x49, 0xde, 0x89, 0xf3, 0x18, 0xc3, 0xad, 0xff, 0x02, 0x00, 0x00, 0xff, 0xff,
+	0xd8, 0xe8, 0xaa, 0xfc, 0x4f, 0x12, 0x00, 0x00,
 }

cmd/protoc-gen-go/testdata/proto2/fields.proto

@@ -96,6 +96,10 @@ message FieldTestMessage {
   optional double default_double_posinf = 404 [default=inf];
   optional double default_double_nan    = 405 [default=nan];
 
+  map<int32, int64>   map_int32_int64    = 500;
+  map<string,Message> map_string_message = 501;
+  map<fixed64,Enum>   map_fixed64_enum   = 502;
+
   enum Enum {
     ZERO = 0;
     ONE = 1;

cmd/protoc-gen-go/testdata/proto3/fields.pb.go

@@ -34,26 +34,29 @@ func (FieldTestMessage_Enum) EnumDescriptor() ([]byte, []int) {
 }
 
 type FieldTestMessage struct {
-	OptionalBool         string                    `protobuf:"bytes,1,opt,name=optional_bool,json=optionalBool,proto3" json:"optional_bool,omitempty"`
-	OptionalEnum         FieldTestMessage_Enum     `protobuf:"varint,2,opt,name=optional_enum,json=optionalEnum,proto3,enum=goproto.protoc.proto3.FieldTestMessage_Enum" json:"optional_enum,omitempty"`
-	OptionalInt32        int32                     `protobuf:"varint,3,opt,name=optional_int32,json=optionalInt32,proto3" json:"optional_int32,omitempty"`
-	OptionalSint32       int32                     `protobuf:"zigzag32,4,opt,name=optional_sint32,json=optionalSint32,proto3" json:"optional_sint32,omitempty"`
-	OptionalUint32       uint32                    `protobuf:"varint,5,opt,name=optional_uint32,json=optionalUint32,proto3" json:"optional_uint32,omitempty"`
-	OptionalInt64        int64                     `protobuf:"varint,6,opt,name=optional_int64,json=optionalInt64,proto3" json:"optional_int64,omitempty"`
-	OptionalSint64       int64                     `protobuf:"zigzag64,7,opt,name=optional_sint64,json=optionalSint64,proto3" json:"optional_sint64,omitempty"`
-	OptionalUint64       uint64                    `protobuf:"varint,8,opt,name=optional_uint64,json=optionalUint64,proto3" json:"optional_uint64,omitempty"`
-	OptionalSfixed32     int32                     `protobuf:"fixed32,9,opt,name=optional_sfixed32,json=optionalSfixed32,proto3" json:"optional_sfixed32,omitempty"`
-	OptionalFixed32      uint32                    `protobuf:"fixed32,10,opt,name=optional_fixed32,json=optionalFixed32,proto3" json:"optional_fixed32,omitempty"`
-	OptionalFloat        float32                   `protobuf:"fixed32,11,opt,name=optional_float,json=optionalFloat,proto3" json:"optional_float,omitempty"`
-	OptionalSfixed64     int64                     `protobuf:"fixed64,12,opt,name=optional_sfixed64,json=optionalSfixed64,proto3" json:"optional_sfixed64,omitempty"`
-	OptionalFixed64      uint64                    `protobuf:"fixed64,13,opt,name=optional_fixed64,json=optionalFixed64,proto3" json:"optional_fixed64,omitempty"`
-	OptionalDouble       float64                   `protobuf:"fixed64,14,opt,name=optional_double,json=optionalDouble,proto3" json:"optional_double,omitempty"`
-	OptionalString       string                    `protobuf:"bytes,15,opt,name=optional_string,json=optionalString,proto3" json:"optional_string,omitempty"`
-	OptionalBytes        []byte                    `protobuf:"bytes,16,opt,name=optional_bytes,json=optionalBytes,proto3" json:"optional_bytes,omitempty"`
-	Optional_Message     *FieldTestMessage_Message `protobuf:"bytes,17,opt,name=optional_Message,json=optionalMessage,proto3" json:"optional_Message,omitempty"`
-	XXX_NoUnkeyedLiteral struct{}                  `json:"-"`
-	XXX_unrecognized     []byte                    `json:"-"`
-	XXX_sizecache        int32                     `json:"-"`
+	OptionalBool         string                               `protobuf:"bytes,1,opt,name=optional_bool,json=optionalBool,proto3" json:"optional_bool,omitempty"`
+	OptionalEnum         FieldTestMessage_Enum                `protobuf:"varint,2,opt,name=optional_enum,json=optionalEnum,proto3,enum=goproto.protoc.proto3.FieldTestMessage_Enum" json:"optional_enum,omitempty"`
+	OptionalInt32        int32                                `protobuf:"varint,3,opt,name=optional_int32,json=optionalInt32,proto3" json:"optional_int32,omitempty"`
+	OptionalSint32       int32                                `protobuf:"zigzag32,4,opt,name=optional_sint32,json=optionalSint32,proto3" json:"optional_sint32,omitempty"`
+	OptionalUint32       uint32                               `protobuf:"varint,5,opt,name=optional_uint32,json=optionalUint32,proto3" json:"optional_uint32,omitempty"`
+	OptionalInt64        int64                                `protobuf:"varint,6,opt,name=optional_int64,json=optionalInt64,proto3" json:"optional_int64,omitempty"`
+	OptionalSint64       int64                                `protobuf:"zigzag64,7,opt,name=optional_sint64,json=optionalSint64,proto3" json:"optional_sint64,omitempty"`
+	OptionalUint64       uint64                               `protobuf:"varint,8,opt,name=optional_uint64,json=optionalUint64,proto3" json:"optional_uint64,omitempty"`
+	OptionalSfixed32     int32                                `protobuf:"fixed32,9,opt,name=optional_sfixed32,json=optionalSfixed32,proto3" json:"optional_sfixed32,omitempty"`
+	OptionalFixed32      uint32                               `protobuf:"fixed32,10,opt,name=optional_fixed32,json=optionalFixed32,proto3" json:"optional_fixed32,omitempty"`
+	OptionalFloat        float32                              `protobuf:"fixed32,11,opt,name=optional_float,json=optionalFloat,proto3" json:"optional_float,omitempty"`
+	OptionalSfixed64     int64                                `protobuf:"fixed64,12,opt,name=optional_sfixed64,json=optionalSfixed64,proto3" json:"optional_sfixed64,omitempty"`
+	OptionalFixed64      uint64                               `protobuf:"fixed64,13,opt,name=optional_fixed64,json=optionalFixed64,proto3" json:"optional_fixed64,omitempty"`
+	OptionalDouble       float64                              `protobuf:"fixed64,14,opt,name=optional_double,json=optionalDouble,proto3" json:"optional_double,omitempty"`
+	OptionalString       string                               `protobuf:"bytes,15,opt,name=optional_string,json=optionalString,proto3" json:"optional_string,omitempty"`
+	OptionalBytes        []byte                               `protobuf:"bytes,16,opt,name=optional_bytes,json=optionalBytes,proto3" json:"optional_bytes,omitempty"`
+	Optional_Message     *FieldTestMessage_Message            `protobuf:"bytes,17,opt,name=optional_Message,json=optionalMessage,proto3" json:"optional_Message,omitempty"`
+	MapInt32Int64        map[int32]int64                      `protobuf:"bytes,500,rep,name=map_int32_int64,json=mapInt32Int64,proto3" json:"map_int32_int64,omitempty" protobuf_key:"varint,1,opt,name=key,proto3" protobuf_val:"varint,2,opt,name=value,proto3"`
+	MapStringMessage     map[string]*FieldTestMessage_Message `protobuf:"bytes,501,rep,name=map_string_message,json=mapStringMessage,proto3" json:"map_string_message,omitempty" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
+	MapFixed64Enum       map[uint64]FieldTestMessage_Enum     `protobuf:"bytes,502,rep,name=map_fixed64_enum,json=mapFixed64Enum,proto3" json:"map_fixed64_enum,omitempty" protobuf_key:"fixed64,1,opt,name=key,proto3" protobuf_val:"varint,2,opt,name=value,proto3,enum=goproto.protoc.proto3.FieldTestMessage_Enum"`
+	XXX_NoUnkeyedLiteral struct{}                             `json:"-"`
+	XXX_unrecognized     []byte                               `json:"-"`
+	XXX_sizecache        int32                                `json:"-"`
 }
 
 func (m *FieldTestMessage) Reset()         { *m = FieldTestMessage{} }
@@ -199,6 +202,27 @@ func (m *FieldTestMessage) GetOptional_Message() *FieldTestMessage_Message {
 	return nil
 }
 
+func (m *FieldTestMessage) GetMapInt32Int64() map[int32]int64 {
+	if m != nil {
+		return m.MapInt32Int64
+	}
+	return nil
+}
+
+func (m *FieldTestMessage) GetMapStringMessage() map[string]*FieldTestMessage_Message {
+	if m != nil {
+		return m.MapStringMessage
+	}
+	return nil
+}
+
+func (m *FieldTestMessage) GetMapFixed64Enum() map[uint64]FieldTestMessage_Enum {
+	if m != nil {
+		return m.MapFixed64Enum
+	}
+	return nil
+}
+
 type FieldTestMessage_Message struct {
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
@@ -209,7 +233,7 @@ func (m *FieldTestMessage_Message) Reset()         { *m = FieldTestMessage_Messa
 func (m *FieldTestMessage_Message) String() string { return proto.CompactTextString(m) }
 func (*FieldTestMessage_Message) ProtoMessage()    {}
 func (*FieldTestMessage_Message) Descriptor() ([]byte, []int) {
-	return fileDescriptor_f1e3ea068187307c, []int{0, 0}
+	return fileDescriptor_f1e3ea068187307c, []int{0, 3}
 }
 func (m *FieldTestMessage_Message) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_FieldTestMessage_Message.Unmarshal(m, b)
@@ -236,33 +260,43 @@ func init() {
 func init() { proto.RegisterFile("proto3/fields.proto", fileDescriptor_f1e3ea068187307c) }
 
 var fileDescriptor_f1e3ea068187307c = []byte{
-	// 440 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x8c, 0x92, 0x4f, 0x6b, 0xdb, 0x40,
-	0x10, 0xc5, 0x3b, 0x89, 0x63, 0xc7, 0x1b, 0xff, 0x91, 0xb7, 0x14, 0x96, 0x9e, 0x96, 0x94, 0xd2,
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-	0x35, 0xba, 0xce, 0x2e, 0x91, 0x69, 0x9c, 0xdb, 0xd5, 0x44, 0x5f, 0x29, 0xac, 0x1a, 0x33, 0x6e,
-	0x4d, 0x71, 0x6f, 0xff, 0x0d, 0x89, 0xb5, 0x2e, 0x7d, 0xbf, 0x64, 0xae, 0xbf, 0xc9, 0x3c, 0x0f,
-	0x95, 0xa4, 0x6f, 0xc8, 0x14, 0x1f, 0x75, 0x82, 0x59, 0x98, 0x3e, 0x44, 0x88, 0x29, 0x03, 0x0e,
-	0x62, 0x1c, 0x4c, 0x9e, 0xc4, 0x15, 0x62, 0x4a, 0x7f, 0x1c, 0x99, 0x64, 0x56, 0xec, 0xd9, 0x05,
-	0x07, 0x31, 0x5b, 0x7e, 0xb4, 0xcf, 0x82, 0xec, 0x3e, 0xc4, 0xbe, 0xcf, 0x8a, 0x7d, 0xbb, 0xb2,
-	0x9c, 0xe8, 0x5b, 0x32, 0x6b, 0x56, 0x26, 0x99, 0x76, 0x97, 0xec, 0x92, 0x83, 0xb8, 0x0a, 0x1a,
-	0xd0, 0xd7, 0x52, 0xa4, 0xef, 0xc8, 0xbc, 0xb1, 0xe5, 0xc6, 0x37, 0xe0, 0x20, 0x16, 0x41, 0xf3,
-	0xf5, 0xcf, 0xe4, 0xc4, 0x58, 0x18, 0xe3, 0x15, 0x07, 0x31, 0x6d, 0x8d, 0xbf, 0x8d, 0xb1, 0x07,
-	0xf6, 0x3d, 0x36, 0xe4, 0x20, 0x2e, 0x3b, 0x60, 0xdf, 0x3b, 0x01, 0xfb, 0x1e, 0x1b, 0x71, 0x10,
-	0xb4, 0x0b, 0xee, 0x19, 0x0b, 0x63, 0xbc, 0xe6, 0x20, 0x06, 0x5d, 0xb0, 0xef, 0xd1, 0x0f, 0x64,
-	0xd1, 0x6e, 0xdc, 0x25, 0x7f, 0x64, 0xec, 0x2e, 0xd9, 0x98, 0x83, 0x98, 0x07, 0x56, 0xb3, 0xb3,
-	0xd6, 0xe9, 0x7b, 0xd2, 0x68, 0x0f, 0x4f, 0x5e, 0xc2, 0x41, 0x8c, 0x82, 0x86, 0xb6, 0xae, 0xad,
-	0xc7, 0x81, 0x76, 0x29, 0x86, 0x9a, 0xdd, 0x70, 0x10, 0x17, 0x6d, 0xa0, 0x75, 0x29, 0x9e, 0xc1,
-	0xfb, 0x1e, 0x9b, 0x70, 0x10, 0x56, 0x1f, 0xef, 0x7b, 0xa7, 0x78, 0xdf, 0x63, 0x53, 0x0e, 0x62,
-	0xd8, 0xc3, 0xf7, 0xf2, 0xc7, 0x58, 0x44, 0xa9, 0x64, 0x33, 0x0e, 0x02, 0xda, 0xfc, 0x5f, 0x2a,
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-	0xa2, 0xbf, 0x5a, 0xe6, 0xcc, 0xe2, 0x20, 0x26, 0x6d, 0xa0, 0x55, 0x29, 0xd2, 0xcd, 0xd1, 0x3f,
-	0xd6, 0x87, 0xc6, 0x16, 0x1c, 0xc4, 0xcd, 0xd2, 0x79, 0xee, 0x5d, 0xd6, 0xb5, 0x0d, 0x55, 0x0b,
-	0xaf, 0xc7, 0x64, 0x54, 0xb7, 0xb7, 0x16, 0x19, 0x54, 0x07, 0x7b, 0x4d, 0x06, 0x9b, 0xfb, 0xe0,
-	0xbb, 0xf5, 0x62, 0xf5, 0x79, 0xf3, 0x49, 0x21, 0xaa, 0x54, 0xda, 0x0a, 0xd3, 0x30, 0x53, 0x36,
-	0x1e, 0x94, 0x53, 0x21, 0x9c, 0xed, 0x3e, 0x36, 0xdd, 0xf6, 0x4e, 0xc9, 0xec, 0x4e, 0xa1, 0xa3,
-	0x65, 0xae, 0xe3, 0x50, 0x87, 0x46, 0x76, 0xa3, 0xa1, 0xa9, 0xff, 0x03, 0x00, 0x00, 0xff, 0xff,
-	0xa9, 0x42, 0xe7, 0xab, 0xb9, 0x03, 0x00, 0x00,
+	// 596 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x9c, 0x94, 0x4b, 0x8f, 0xd3, 0x3c,
+	0x18, 0x85, 0x3f, 0x4f, 0x7a, 0x99, 0xba, 0xb7, 0xd4, 0xf3, 0x8d, 0x64, 0xcd, 0xca, 0x1a, 0x84,
+	0x30, 0x82, 0x49, 0xa5, 0x36, 0x8a, 0x60, 0x46, 0x48, 0xa8, 0xa2, 0x95, 0x58, 0x20, 0x44, 0x80,
+	0x4d, 0x37, 0x55, 0xda, 0xba, 0x51, 0x44, 0x12, 0x57, 0x8d, 0x83, 0xe8, 0x4f, 0xe2, 0xff, 0x01,
+	0x6b, 0x14, 0x3b, 0xcd, 0xad, 0x5d, 0x4c, 0x59, 0xd9, 0x3e, 0x3d, 0x7d, 0x9f, 0x1c, 0xfb, 0xb5,
+	0xe1, 0xd5, 0x76, 0xc7, 0x05, 0x1f, 0x0f, 0x37, 0x1e, 0xf3, 0xd7, 0x91, 0x21, 0x57, 0xe8, 0xda,
+	0xe5, 0x72, 0xa2, 0x96, 0x2b, 0x35, 0x8c, 0x6f, 0x7f, 0xb6, 0xa1, 0x3e, 0x4b, 0x7c, 0x5f, 0x58,
+	0x24, 0x3e, 0xb0, 0x28, 0x72, 0x5c, 0x86, 0x9e, 0xc0, 0x2e, 0xdf, 0x0a, 0x8f, 0x87, 0x8e, 0xbf,
+	0x58, 0x72, 0xee, 0x63, 0x40, 0x00, 0x6d, 0xd9, 0x9d, 0x83, 0x38, 0xe1, 0xdc, 0x47, 0x9f, 0x0a,
+	0x26, 0x16, 0xc6, 0x01, 0xbe, 0x20, 0x80, 0xf6, 0x46, 0x2f, 0x8d, 0x93, 0x20, 0xa3, 0x0a, 0x31,
+	0xa6, 0x61, 0x1c, 0xe4, 0x25, 0x93, 0x15, 0x7a, 0x0a, 0x7b, 0x59, 0x49, 0x2f, 0x14, 0xe3, 0x11,
+	0xd6, 0x08, 0xa0, 0x75, 0x3b, 0x03, 0xbd, 0x4f, 0x44, 0xf4, 0x0c, 0xf6, 0x33, 0x5b, 0xa4, 0x7c,
+	0x35, 0x02, 0xe8, 0xc0, 0xce, 0xfe, 0xfd, 0xd9, 0x3b, 0x32, 0xc6, 0xca, 0x58, 0x27, 0x80, 0x76,
+	0x73, 0xe3, 0x57, 0x65, 0xac, 0x80, 0x2d, 0x13, 0x37, 0x08, 0xa0, 0x5a, 0x09, 0x6c, 0x99, 0x47,
+	0x60, 0xcb, 0xc4, 0x4d, 0x02, 0x28, 0x2a, 0x83, 0x2b, 0xc6, 0x58, 0x19, 0x2f, 0x09, 0xa0, 0xb5,
+	0x32, 0xd8, 0x32, 0xd1, 0x0b, 0x38, 0xc8, 0x2b, 0x6e, 0xbc, 0x1f, 0x6c, 0x3d, 0x1e, 0xe1, 0x16,
+	0x01, 0xb4, 0x6f, 0xeb, 0x59, 0xcd, 0x54, 0x47, 0xcf, 0x61, 0xa6, 0x2d, 0x0e, 0x5e, 0x48, 0x00,
+	0x6d, 0xda, 0x19, 0x6d, 0x96, 0x5a, 0x8b, 0x81, 0x36, 0x3e, 0x77, 0x04, 0x6e, 0x13, 0x40, 0x2f,
+	0xf2, 0x40, 0xb3, 0x44, 0x3c, 0x81, 0xb7, 0x4c, 0xdc, 0x21, 0x80, 0xea, 0x55, 0xbc, 0x65, 0x1e,
+	0xe3, 0x2d, 0x13, 0x77, 0x09, 0xa0, 0x8d, 0x0a, 0xbe, 0x92, 0x7f, 0xcd, 0xe3, 0xa5, 0xcf, 0x70,
+	0x8f, 0x00, 0x0a, 0xf2, 0xfc, 0xef, 0xa4, 0x5a, 0xde, 0x51, 0xb1, 0xf3, 0x42, 0x17, 0xf7, 0x65,
+	0xaf, 0xe5, 0x3b, 0x2a, 0xd5, 0x52, 0xa0, 0xe5, 0x5e, 0xb0, 0x08, 0xeb, 0x04, 0xd0, 0x4e, 0x1e,
+	0x68, 0x92, 0x88, 0x68, 0x5e, 0xf8, 0xc6, 0xb4, 0xd1, 0xf0, 0x80, 0x00, 0xda, 0x1e, 0x0d, 0x1f,
+	0xdb, 0x97, 0xe9, 0x98, 0x87, 0x3a, 0xdc, 0x8a, 0x15, 0xec, 0x07, 0xce, 0x56, 0x35, 0x66, 0xda,
+	0x25, 0xbf, 0x34, 0xa2, 0xd1, 0xf6, 0xe8, 0xfe, 0xd1, 0xb5, 0x9d, 0xad, 0x6c, 0x61, 0xd9, 0x4e,
+	0xd3, 0x50, 0xec, 0xf6, 0x76, 0x37, 0x28, 0x6a, 0xc8, 0x87, 0x28, 0x81, 0xa8, 0xbd, 0x58, 0x04,
+	0x69, 0x84, 0xdf, 0x8a, 0xf3, 0xe6, 0x0c, 0x8e, 0xda, 0xb7, 0x54, 0x50, 0x28, 0x3d, 0xa8, 0xc8,
+	0x68, 0x03, 0x13, 0xed, 0x70, 0x9a, 0xea, 0x1a, 0xff, 0x51, 0xac, 0x87, 0x33, 0x58, 0xe9, 0xb1,
+	0x27, 0x77, 0x58, 0x91, 0x7a, 0x41, 0x49, 0xbc, 0x79, 0x0b, 0xd1, 0x71, 0x74, 0xa4, 0x43, 0xed,
+	0x1b, 0xdb, 0xcb, 0xc7, 0xa5, 0x6e, 0x27, 0x53, 0xf4, 0x3f, 0xac, 0x7f, 0x77, 0xfc, 0x98, 0xc9,
+	0xb7, 0x44, 0xb3, 0xd5, 0xe2, 0xfe, 0xe2, 0x15, 0xb8, 0x11, 0xf0, 0xfa, 0x64, 0xa8, 0x62, 0x91,
+	0x96, 0x2a, 0x32, 0x2d, 0x16, 0xf9, 0x87, 0x83, 0x2f, 0x50, 0x39, 0xbc, 0x3a, 0x11, 0xaf, 0xc8,
+	0x6c, 0x28, 0xe6, 0xa4, 0xc8, 0x3c, 0xf7, 0x11, 0x2c, 0x00, 0x5b, 0xb0, 0x99, 0xfe, 0x74, 0xab,
+	0xc3, 0x9a, 0x7c, 0x14, 0x2f, 0x61, 0x6d, 0x3e, 0xb5, 0x3f, 0xea, 0xff, 0x4d, 0x1e, 0xe6, 0xaf,
+	0x5d, 0xce, 0x5d, 0x9f, 0x19, 0x2e, 0xf7, 0x9d, 0xd0, 0x35, 0xf8, 0xce, 0x1d, 0xca, 0xca, 0xc3,
+	0x55, 0xb0, 0x56, 0xb3, 0xd5, 0x9d, 0xcb, 0xc2, 0x3b, 0x97, 0x0f, 0x05, 0x8b, 0xc4, 0xda, 0x11,
+	0x8e, 0x92, 0xc7, 0xcb, 0x86, 0x1a, 0xff, 0x06, 0x00, 0x00, 0xff, 0xff, 0x3e, 0xd2, 0xfc, 0xf5,
+	0x1d, 0x06, 0x00, 0x00,
 }

cmd/protoc-gen-go/testdata/proto3/fields.proto

@@ -27,6 +27,10 @@ message FieldTestMessage {
   bytes    optional_bytes    = 16;
   Message  optional_Message  = 17;
 
+  map<int32, int64>   map_int32_int64    = 500;
+  map<string,Message> map_string_message = 501;
+  map<fixed64,Enum>   map_fixed64_enum   = 502;
+
   enum Enum { ZERO = 0; }
   message Message {}
 }

protogen/protogen.go

@@ -400,6 +400,9 @@ func newFile(gen *Plugin, p *descpb.FileDescriptorProto, packageName GoPackageNa
 	for i, edescs := 0, desc.Enums(); i < edescs.Len(); i++ {
 		f.Enums = append(f.Enums, newEnum(gen, f, nil, edescs.Get(i)))
 	}
+	for _, message := range f.Messages {
+		message.init(gen)
+	}
 	return f, nil
 }
 
@@ -507,6 +510,20 @@ func newMessage(gen *Plugin, f *File, parent *Message, desc protoreflect.Message
 	return message, nil
 }
 
+func (message *Message) init(gen *Plugin) error {
+	for _, child := range message.Messages {
+		if err := child.init(gen); err != nil {
+			return err
+		}
+	}
+	for _, field := range message.Fields {
+		if err := field.init(gen); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 // A Field describes a message field.
 type Field struct {
 	Desc protoreflect.FieldDescriptor
@@ -530,23 +547,28 @@ func newField(gen *Plugin, f *File, message *Message, desc protoreflect.FieldDes
 		},
 		Path: pathAppend(message.Path, messageFieldField, int32(desc.Index())),
 	}
+	return field, nil
+}
+
+func (field *Field) init(gen *Plugin) error {
+	desc := field.Desc
 	switch desc.Kind() {
 	case protoreflect.MessageKind, protoreflect.GroupKind:
 		mname := desc.MessageType().FullName()
 		message, ok := gen.messagesByName[mname]
 		if !ok {
-			return nil, fmt.Errorf("field %v: no descriptor for type %v", desc.FullName(), mname)
+			return fmt.Errorf("field %v: no descriptor for type %v", desc.FullName(), mname)
 		}
 		field.MessageType = message
 	case protoreflect.EnumKind:
-		ename := desc.EnumType().FullName()
+		ename := field.Desc.EnumType().FullName()
 		enum, ok := gen.enumsByName[ename]
 		if !ok {
-			return nil, fmt.Errorf("field %v: no descriptor for enum %v", desc.FullName(), ename)
+			return fmt.Errorf("field %v: no descriptor for enum %v", desc.FullName(), ename)
 		}
 		field.EnumType = enum
 	}
-	return field, nil
+	return nil
 }
 
 // An Enum describes an enum.