Make new destination slice when length doesn't match.

decode.go

@@ -308,7 +308,7 @@ func (md *MetaData) unifySlice(data interface{}, rv reflect.Value) error {
 		return badtype("slice", data)
 	}
 	sliceLen := datav.Len()
-	if rv.IsNil() {
+	if rv.IsNil() || rv.Len() != datav.Len() {
 		rv.Set(reflect.MakeSlice(rv.Type(), sliceLen, sliceLen))
 	}
 	return md.unifySliceArray(datav, rv)

decode_test.go

@@ -468,6 +468,15 @@ type ingredient struct {
 	Name string
 }
 
+func TestDecodeToEmptySlice(t *testing.T) {
+	s := struct{ Test []string }{Test: []string{}}
+
+	_, err := Decode(`Test = ["test"]`, &s)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 func ExampleMetaData_PrimitiveDecode() {
 	var md MetaData
 	var err error