Function seek_pattern_is_useful 

pub fn seek_pattern_is_useful(pattern: &str) -> bool

Returns true if pattern contains at least one character that provides useful filtering (i.e. a literal character, character class, or anchor rather than just wildcards/quantifiers).

This is a conservative approximation: any pattern containing [, \, ^, $, or an alphanumeric character is considered useful. The primary goal is to reject fully unconstrained patterns such as .*.