fix for issue 209: dont import types when its not used

Makefile

@@ -101,6 +101,7 @@ regenerate:
 	make -C test/nopackage regenerate
 	make -C test/types regenerate
 	make -C test/proto3extension regenerate
+	make -C test/stdtypes regenerate
 	make gofmt
 
 tests:

protoc-gen-gogo/generator/generator.go

@@ -1958,7 +1958,9 @@ func (g *Generator) GoMapType(d *Descriptor, field *descriptor.FieldDescriptorPr
 		if !gogoproto.IsNullable(m.ValueAliasField) {
 			valType = strings.TrimPrefix(valType, "*")
 		}
-		g.RecordTypeUse(m.ValueAliasField.GetTypeName())
+		if !gogoproto.IsStdTime(field) && !gogoproto.IsStdDuration(field) {
+			g.RecordTypeUse(m.ValueAliasField.GetTypeName())
+		}
 	default:
 		if gogoproto.IsCustomType(m.ValueAliasField) {
 			if !gogoproto.IsNullable(m.ValueAliasField) {
@@ -2174,7 +2176,9 @@ func (g *Generator) generateMessage(message *Descriptor) {
 
 		g.PrintComments(fmt.Sprintf("%s,%d,%d", message.path, messageFieldPath, i))
 		g.P(fieldName, "\t", typename, "\t`", tag, "`")
-		g.RecordTypeUse(field.GetTypeName())
+		if !gogoproto.IsStdTime(field) && !gogoproto.IsStdDuration(field) {
+			g.RecordTypeUse(field.GetTypeName())
+		}
 	}
 	if len(message.ExtensionRange) > 0 {
 		if gogoproto.HasExtensionsMap(g.file.FileDescriptorProto, message.DescriptorProto) {
@@ -2403,7 +2407,9 @@ func (g *Generator) generateMessage(message *Descriptor) {
 			_, wiretype := g.GoType(message, field)
 			tag := "protobuf:" + g.goTag(message, field, wiretype)
 			g.P("type ", oneofTypeName[field], " struct{ ", fieldNames[field], " ", fieldTypes[field], " `", tag, "` }")
-			g.RecordTypeUse(field.GetTypeName())
+			if !gogoproto.IsStdTime(field) && !gogoproto.IsStdDuration(field) {
+				g.RecordTypeUse(field.GetTypeName())
+			}
 		}
 		g.P()
 		for _, field := range message.Field {

test/stdtypes/Makefile

@@ -0,0 +1,37 @@
+# Protocol Buffers for Go with Gadgets
+#
+# Copyright (c) 2016, The GoGo Authors. All rights reserved.
+# http://github.com/gogo/protobuf
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+regenerate:
+	go install github.com/gogo/protobuf/protoc-min-version
+	go install github.com/gogo/protobuf/protoc-gen-gogo
+	protoc-min-version --version="3.0.0" --gogo_out=\
+	Mgoogle/protobuf/duration.proto=github.com/gogo/protobuf/types,\
+	Mgoogle/protobuf/timestamp.proto=github.com/gogo/protobuf/types\
+	:. \
+	--proto_path=../../../../../:../../protobuf/:. stdtypes.proto
+