Function regex_syntax::is_meta_character

pub fn is_meta_character(c: char) -> bool

Returns true if the given character has significance in a regex.

These are the only characters that are allowed to be escaped, with one exception: an ASCII space character may be escaped when extended mode (with the x flag) is enabled. In particular, is_meta_character(' ') returns false.

Note that the set of characters for which this function returns true or false is fixed and won’t change in a semver compatible release.