// Phase 6 / issue 0054 — generic-struct → parameterized-protocol erasure.
//   - A generic-struct impl method `self: *Box` now resolves `self.field` to the
//     concrete INSTANCE (the template name binds to the instance type), so
//     `self.x` works (was "field not found on type 'Box'").
//   - `xx c` erases a generic-struct instance (`Combined__i64_i64`) to a
//     parameterized protocol (`VL(i64)`) via the generic
//     `impl VL($R) for Combined($R, ..$Ts)`: the thunk monomorphizes the
//     template method for the instance and dispatch works (was a trap).

#import "modules/std.sx";

VL :: protocol(T: Type) { get :: () -> T; }
IntCell :: struct { v: i64; }
impl VL(i64) for IntCell { get :: (self: *IntCell) -> i64 => self.v; }

Combined :: struct($R: Type, ..$Ts: []Type) {
    sources: (..VL(Ts));
    value:   $R;
}
impl VL($R) for Combined($R, ..$Ts) { get :: (self: *Combined) -> $R => self.value; }

make :: (..sources: VL) -> VL(i64) {
    c : Combined(i64, ..sources.T) = ---;
    c.value = 99;
    c.sources = (..sources);
    return xx c;                 // Combined__i64_i64 -> VL(i64)
}

main :: () -> i32 {
    r := make(IntCell.{ v = 1 });
    print("{}\n", r.get());      // 99 (dispatch through the erased Combined)
    0
}