// A genuinely-undeclared type name used as a field type inside a MAIN-file
// GENERIC struct must emit a clean "unknown type" diagnostic, not silently
// compile.
//
// The `UnknownTypeChecker` used to SKIP generic structs entirely ("their field
// types reference the struct's own `$T`, resolved at instantiation"). That skip
// was too broad: a field type like `bad: MissingType` — which is NOT a type
// param and names no declared type — fell through the type leaf's empty-struct
// stub and the struct silently compiled, mis-sizing every downstream load.
//
// The checker now walks generic-struct fields with the struct's own type params
// (`$T`) in scope: `good: T` resolves (it IS a param) while `bad: MissingType`
// is reported. A value-param position (a `Vector` lane count, a `$N: u32` arg)
// is still skipped, so a valid generic struct keeps compiling unchanged.
//
// Expected: `error: unknown type 'MissingType'` pointing at the field; exit 1.
// Regression (stdlib E3).
#import "modules/std.sx";

Box :: struct($T: Type) {
    good: T;
    bad: MissingType;
}

main :: () -> s32 {
    b : Box(s64) = .{ good = 7, bad = 0 };
    print("{}\n", b.good);
    return 0;
}