void (String[] args) { List<List<String>> x = null; foo<error descr="Ambiguous method call: both 'A.foo(List<List<String>>)' and 'A.foo(Collection<List<String>>)' match">(x)</error>; foo<error descr="Ambiguous method call: both 'A.foo(List<Object>)' and 'A.foo(Collection<List<?>>)' match">(null)</error>; }