Talk:DIP32

About $identifier

Why not require normal declaration syntax, when a variable should be declared in unpacking?

Suggested in DIP:

switch (tup) {
    case {1, 2}:
    case {$, 2}:
    case {1, x}:
    default:
}
// -----------------------------
int x = 1;
if (auto {$x, y} = coord) { ... }

My suggestion:

switch (tup) {
    case {1, 2}:
    case {$, 2}:
    case {1, auto x}:
    default:
}
// -----------------------------
int x = 1;
if ({x, auto y} = coord) { ... }

This would be more consistent with how if usually works (expression syntax => use existing variable, declaration syntax => declare variable initialized with the value of the comparison), doesn't require this special syntax which is used nowhere else in the language, and makes it obvious that a declaration takes place.

It also allows to use unpacking everywhere:

int x;
{x, int y} = tup;

Variable declaration in case statements

Care must be taken when variable declaration is used in combination with fall through / goto case in case statements:

switch (tup) {
    case {1, 2}:
    case {$, 2}:
        goto case;
    case {1, x}:
        // what is x if tup == {1, 2}?
}

Tuple Slicing?

If you want you can also add a slicing syntax for tuples:

auto t1 = {10, 20.5, "foo"};
auto t2 = t1[1 .. $];

Return ref value in tuple?

This is currently not possible with Phobos tuples:

{ref int, int} foo(ref int x) {
    return tuple(x, 5);
}
void main() {}

Built-in tuples should avoid Phobos Tuple const problems

Like this one:

void main() {
    import std.typecons: Tuple;
    Tuple!int t1;
    alias T = const Tuple!int;
    T t2;
    t1 = t2;  // OK
    t1 = T(); // Error
}