import java.util.*; class BugReportLambdaSquiggles<T> { private T t; public <V> List<V> flatMap(Mapper<T, List<V>> mapper) { return mapper.map(t); } static void bar( BugReportLambdaSquiggles<Integer> x) { x.flatMap(t1 -> new ArrayList<String>(t1)); x.flatMap(t1 -> new ArrayList<>(t1)); } interface Mapper<T, U> { U map(T t); } }