Reflect actual slice type in TreeFromMap (#145)

* Reflect actual slice type in TreeFromMap
* Fix writeTo for slices tomlValues

Fixes #143

tomltree_write.go

@@ -8,6 +8,7 @@ import (
 	"strconv"
 	"strings"
 	"time"
+	"reflect"
 )
 
 // encodes a string to a TOML-compliant string value
@@ -60,9 +61,14 @@ func tomlValueStringRepresentation(v interface{}) (string, error) {
 		return value.Format(time.RFC3339), nil
 	case nil:
 		return "", nil
-	case []interface{}:
+	}
+
+	rv := reflect.ValueOf(v)
+
+	if rv.Kind() == reflect.Slice {
 		values := []string{}
-		for _, item := range value {
+		for i := 0; i < rv.Len(); i++ {
+			item := rv.Index(i).Interface()
 			itemRepr, err := tomlValueStringRepresentation(item)
 			if err != nil {
 				return "", err
@@ -70,9 +76,8 @@ func tomlValueStringRepresentation(v interface{}) (string, error) {
 			values = append(values, itemRepr)
 		}
 		return "[" + strings.Join(values, ",") + "]", nil
-	default:
-		return "", fmt.Errorf("unsupported value type %T: %v", value, value)
 	}
+	return "", fmt.Errorf("unsupported value type %T: %v", v, v)
 }
 
 func (t *TomlTree) writeTo(w io.Writer, indent, keyspace string, bytesCount int64) (int64, error) {