tuple move constructor

[Jonathan Wakely]

On 20 April 2016 at 21:42, Marc Glisse wrote:
> Hello,
>
> does anyone remember why the move constructor of _Tuple_impl is not
> defaulted? The attached patch does not cause any test to fail (whitespace
> kept to avoid line number changes). Maybe something about tuples of
> references?

I don't know/remember why. It's possible it was to workaround a
front-end bug that required it, or maybe just a mistake and it should
always have been defaulted.