I dun a DIP, possibly the best DIP ever

[Manu]

On Fri, Apr 24, 2020 at 11:00 PM Nick Treleaven via Digitalmars-d <
digitalmars-d at puremagic.com> wrote:

> On Friday, 24 April 2020 at 08:04:29 UTC, Walter Bright wrote:
> > On 4/24/2020 1:03 AM, Walter Bright wrote:
> >> On 4/24/2020 12:10 AM, Manu wrote:
> >>>    alias Tup = AliasSeq!(0, 2, 3);
> >>>    void fun(int);
> >>>    fun(Tup);  // scalar argument receives tuple, it can
> >>> expand, so: fun(0), fun(1), fun(2)
> >>
> >> Write it as:
> >>
> >>      Tup.fun();
> >
> > Incidentally, belay that. That will currently produce: fun(0,
> > 2, 3);
>
> This syntax is an unfortunate inconsistency with your proposal,
> but how often is variadic UFCS used ATM? Its existence has been
> pointed out in a NG reply before (I think by Timon), but it
> seemed to surprise people. Perhaps it could be deprecated - use
> fun(Tup) instead. The latter is more intuitive as people tend to
> think UFCS is for the first argument, not multiple arguments. The
> spec doesn't seem to suggest variadic UFCS is supported:
>
> https://dlang.org/spec/function.html#pseudo-member
>
> > Of course,
> >
> >     fun(1, Tup);
> >
> > cannot be rewritten in this way
>
> AliasSeq!(1, Tup).fun(); // fun(1); fun(0); fun(2); fun(3);
>

I pointed out earlier, and I'll point out again, that Walter's proposal can
not be applied to ANY parameter lists, because overloading and possibility
for hijacking.

  int fun(int);
  fun(Tup);  ->  fun(Tup[0]), fun(Tup[1]), fun(Tup[2])

This looks intuitive, but then someone adds:

  void fun(int, int, int);

Or maybe it was already there...
So, a 2 or >=4 len tuple could expand, but a 3-len tuple would call the
3-arg overload.
What if the function has variadic args?
Hijacking possibility just wipes this whole thing off the table.

The ambiguities in Walter's suggestion are impossible to reconcile in a
uniform and satisfying way. That's exactly why I moved away from that idea
and towards an explicit expression. It's the only way.
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