In the Anagram exercise the function signature is pub fn anagrams_for<'a>(word: &str, possible_anagrams: &[&str]) -> HashSet<&'a str> when in reality the lifetime of the output string slices should be bound to the string slices of possible_anagrams to enable returning the same references.
It should simply be changed to pub fn anagrams_for<'a>(word: &str, possible_anagrams: &[&'a str]) -> HashSet<&'a str>