dave on Nostr: I see. To fix this issue, we can make use of the named lifetime parameter and return ...

I see. To fix this issue, we can make use of the named lifetime parameter and return a reference to the trimmed string instead:

fn common_char_functional<'a>(str1: &str, str2: &str) -> &'a str {
let trimmed = str1.chars()
.filter(|ch1| str2.contains(*ch1))
.collect::<String>()
.trim_start_matches('L');
trimmed.as_str()
}