Reflect actual slice type in TreeFromMap (#145)

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

Fixes #143

tomltree_create_test.go

@@ -3,6 +3,7 @@ package toml
 import (
 	"testing"
 	"time"
+	"strconv"
 )
 
 type customString string
@@ -21,20 +22,19 @@ func validate(t *testing.T, path string, object interface{}) {
 		}
 	case []*TomlTree:
 		for index, tree := range o {
-			validate(t, path+"."+string(index), tree)
+			validate(t, path+"."+strconv.Itoa(index), tree)
 		}
 	case *tomlValue:
 		switch o.value.(type) {
 		case int64, uint64, bool, string, float64, time.Time,
 			[]int64, []uint64, []bool, []string, []float64, []time.Time:
-			return // ok
 		default:
 			t.Fatalf("tomlValue at key %s containing incorrect type %T", path, o.value)
 		}
 	default:
 		t.Fatalf("value at key %s is of incorrect type %T", path, object)
 	}
-	t.Log("validation ok", path)
+	t.Logf("validation ok %s as %T", path, object)
 }
 
 func validateTree(t *testing.T, tree *TomlTree) {
@@ -103,3 +103,24 @@ func TestTomlTreeCreateToTreeInvalidTableGroupType(t *testing.T) {
 		t.Fatalf("expected error %s, got %s", expected, err.Error())
 	}
 }
+
+func TestRoundTripArrayOfTables(t *testing.T) {
+	orig := "\n[[stuff]]\n  name = \"foo\"\n  things = [\"a\",\"b\"]\n"
+	tree, err := Load(orig)
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+
+	m := tree.ToMap()
+
+	tree, err = TreeFromMap(m)
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+	want := orig
+	got := tree.String()
+
+	if got != want {
+		t.Errorf("want:\n%s\ngot:\n%s", want, got)
+	}
+}