// Variadic heterogeneous type packs — step 3: `$args[$i]` in
// fn-pointer type literals.
//
// `(*void, $args[0]) -> $args[1]` is the shape step 5's generic
// `Into(Block) for Closure(..$args) -> $R` body needs for its
// trampoline:
//   typed_fn : (*void, $args[0], $args[1], ...) -> $R =
//       xx block_self.sx_fn;
// — the trampoline's invoke slot is typed against the pack
// positions to bridge the Block ABI to the sx closure.
//
// This test exercises the same plumbing on a smaller scale: a
// local var with a fn-pointer type whose param + return types
// both interpolate through `$args[$i]`.

#import "modules/std.sx";

// Two concrete handlers that match the per-mono fn-pointer shape.
double_i64 :: (env: *void, x: i64) -> i64 => x * 2;

via_fnptr :: (..$args) -> $args[1] {
    fp : (*void, $args[0]) -> $args[1] = double_i64;
    return fp(null, args[0]);
}

main :: () -> i32 {
    n := via_fnptr(7, 0);  // (i64, i64) → fp : (*void, i64) -> i64
    print("{}\n", n);
    return 0;
}