// Phase 4.2 (core) — a generic struct with a pack type-param `..$Ts: []Type`
// and a pack-shaped tuple field `(..$Ts)`. Each instantiation binds the
// remaining type args as the pack, so the field is a tuple of those per-position
// types. Storing the whole tuple field and reading its elements both work.

#import "modules/std.sx";

Box :: struct($R: Type, ..$Ts: []Type) {
    r:    $R;
    pair: (..$Ts);   // tuple of the pack's element types
}

main :: () -> s32 {
    // Box(s64, s32, string): R=s64, Ts=[s32, string], pair: (s32, string).
    a : Box(s64, s32, string) = ---;
    a.r = 7;
    a.pair = (42, "hi");                 // whole-tuple field store
    print("a: r={} 0={} 1={}\n", a.r, a.pair.0, a.pair.1);

    // A different shape → a different per-position tuple field.
    b : Box(bool, string, bool) = ---;   // Ts=[string, bool], pair: (string, bool)
    b.pair = ("x", true);
    print("b: 0={} 1={}\n", b.pair.0, b.pair.1);
    0;
}