What does "(this This)" mean in member function templates?

[rikki cattermole]

On 12/02/2018 8:35 AM, Nathan S. wrote:
> For example in std.container.rbtree:
> 
> ---
>      auto equalRange(this This)(Elem e)
>      {
>          auto beg = _firstGreaterEqual(e);
>          alias RangeType = RBRange!(typeof(beg));
>          if (beg is _end || _less(e, beg.value))
>              // no values are equal
>              return RangeType(beg, beg);
>          static if (allowDuplicates)
>          {
>              return RangeType(beg, _firstGreater(e));
>          }
>          else
>          {
>              // no sense in doing a full search, no duplicates are allowed,
>              // so we just get the next node.
>              return RangeType(beg, beg.next);
>          }
>      }
> ---

https://dlang.org/spec/template.html#TemplateThisParameter