// superclass mapping should take precedence.
        return;
      }
      // First, check whether var -> arg forms a cycle
      for (Type t = arg; t != null; t = mappings.get(TypeVariableKey.forLookup(t))) {
        if (var.equalsType(t)) {
          // cycle detected, remove the entire cycle from the mapping so that
          // each type variable resolves deterministically to itself.

        // superclass mapping should take precedence.
        return;
      }
      // First, check whether var -> arg forms a cycle
      for (Type t = arg; t != null; t = mappings.get(TypeVariableKey.forLookup(t))) {
        if (var.equalsType(t)) {
          // cycle detected, remove the entire cycle from the mapping so that
          // each type variable resolves deterministically to itself.

                    .createContainerCapsule(this, context, createCoreExtensionSelector());
            context.closeables.add(context::closeContainer);
            context.lookup = context.containerCapsule.getLookup();
        } else {
            context.containerCapsule.updateLogging(context);
        }
    }

    protected CoreExtensionSelector<C> createCoreExtensionSelector() {