Fix bug in format auto spec indexing.
@@ -856,7 +856,7 @@ impl FormatString {
auto_argument_index += 1;
arguments
.args
- .get(auto_argument_index)
+ .get(auto_argument_index - 1)
.cloned()
.ok_or_else(|| vm.new_index_error("tuple index out of range".to_owned()))
}
