DIP19: Remove comma operator from D and provision better syntactic support for tuples

[foobar]

On Tuesday, 25 September 2012 at 21:02:49 UTC, Andrei 
Alexandrescu wrote:
>
> I agree. That's why I want to take the minimum amount of steps 
> to make library tuples work. That minimum amount may be 1, i.e. 
> just implement deconstruction.
>
> Andrei

Library tuples have broken semantics.
Tuples supposed to have _structural_ typing which AFAIK can only 
be correctly implemented in language.

import std.typecons.TypeTuple;

struct MyTuple(T...)() {}

auto libTup = tuple(123, "hello");
MyTuple myTup = libTup; // broken

This is broken cause structs in D are nominally typed and even 
though both pack the same inner-types, they are not equal.
The problem with the lib solution is the confusion and broken 
semantics, _not_ the "tuple()" syntax. Sure, it's long and 
annoying to type for a [should be] common construct, but tuple 
*is* clear and readable, as you pointed out yourself. So syntax 
wise, I'm fine with both tuple(...) and a shorter syntax with 
some sort of parens-like character. But please, let's get at 
least the semantics absolutely right.

I don't have a good suggestion how to fix this with no or minimal 
code breakage, but I don't thing that adding broken features the 
the mix helps any.