Function has_irregular_lowercase 

pub fn has_irregular_lowercase(text: &str) -> bool

Returns whether lowercasing text as a whole can produce tokens that lowercasing each token of text doesn’t, which matches_term(lower(col), ..) and lower(col) LIKE .. rely on. Every other character lowercases to one character of the same class, but U+0130 and U+212A change length or class, and Σ lowercases depending on the characters after it.