// E6b-R — own-wins-over-flat at the NEW use surfaces route-all funnels through the
// source-aware engine. `main` flat-imports `dep.sx` (which authors `Box { a }`) AND
// authors its OWN `Box { m }`; the field sets are DISJOINT, so the observable is
// field access: `.m` typechecks only against main's `Box`, `.a` only against dep's.
//
// `WrapU` is authored only by `main`, so its union field type `Box` resolves at
// registration (`registerUnionDecl` → the source-aware body builder, E6b-R C1) to
// MAIN's `Box`. Accessing `w.b.m` therefore typechecks, while `dep_box` uses dep's
// DISTINCT `Box { a }`.
//
// Fail-before (pre-E6b-R): `registerUnionDecl` built the union body through the
// stateless `type_bridge.buildUnionInfo`, whose `findByName` short-circuit bound
// the global last-wins `Box`. If dep's `Box { a }` won the slot, `WrapU.b` was
// dep's `Box` and `w.b.m` was a hard "field not found" — silently wrong nominal.
// Pass-after: the union field is main's own `Box`, `w.b.m` resolves, exit 0.

#import "modules/std.sx";
#import "0816-route-all-new-surfaces-own-wins/dep.sx";

Box :: struct { m: s32; }

WrapU :: union { b: Box; n: s32; }

main :: () -> s32 {
    w : WrapU = ---;
    w.b.m = 5;
    print("own={} dep={}\n", w.b.m, dep_box());
    0
}