Why does the prettyprint of std::tuple start with [1]?

[Paul Smith]

On Sun, 2021-06-13 at 09:49 -0400, Paul Smith wrote:
> Am I the only one to be confused by the fact that the pretty-printer
> for std::tuple values starts indexing at 1 instead of 0?
> 
> (gdb) p info
> $1 = (const std::tuple<TestType, DataType> &) @0x7fffffffd550: {
>   param = std::tuple containing = {
>     [1] = TestType::OneTest,
>     [2] = DataType::SomeData
>   },
>   index = 2
> }
> 
> Why aren't the indexes on the left numbered [0] and [1],
> corresponding
> to the values used with std::get(), instead of [1] and [2]?

Hm, maybe this belongs on the GCC mailing list instead of here.