add comment struct

comment/comment.go

@@ -0,0 +1,5 @@
+package comment
+
+type Comment interface {
+	String() string
+}

comment/doc_comment.go

@@ -0,0 +1,15 @@
+package comment
+
+type DocComment struct {
+	value string
+}
+
+func NewDocComment(value string) Comment {
+	return &DocComment{
+		value,
+	}
+}
+
+func (c *DocComment) String() string {
+	return c.value
+}

comment/plain_comment.go

@@ -0,0 +1,15 @@
+package comment
+
+type PlainComment struct {
+	value string
+}
+
+func NewPlainComment(value string) Comment {
+	return &PlainComment{
+		value,
+	}
+}
+
+func (c *PlainComment) String() string {
+	return c.value
+}