I get the following warning :

[0,123s][warning][class,preload] Preloading of class Main$Trampo during loading of class Main$Trampo$SubTr (cause: field type in LoadableDescriptors attribute) failed : java/lang/ClassCircularityError

while trying to *run* this code (it compiles fine) :

value record Trampo<A>(A a, SubTr<?, A> sub) {

    value record SubTr<A, B>(Trampo<A> stack, F<A, Trampo<B>> cont) {}
}

void main() {
    final var tr = new Trampo<>(1, new Trampo.SubTr<>(new Trampo<>(0, null), i -> new Trampo<>(i + 1, null)));

    IO.println("TRAMPO => %s".formatted(tr));
}

This is on java :

openjdk version "26-jep401ea2" 2026-03-17
OpenJDK Runtime Environment (build 26-jep401ea2+1-1)
OpenJDK 64-Bit Server VM (build 26-jep401ea2+1-1, mixed mode, sharing)