Method is_lookaround_prefix

regex/regex-syntax/src/ast/parse.rs:523–528

Returns true if and only if the parser is positioned at a look-around prefix. The conditions under which this returns true must always correspond to a regular expression that would otherwise be consider invalid. This should only be called immediately after parsing the opening of a group or a set of flags.

(&self)

    /// This should only be called immediately after parsing the opening of
    /// a group or a set of flags.
    fn is_lookaround_prefix(&self) -> bool {
        self.bump_if("?=")
        || self.bump_if("?!")
        || self.bump_if("?<=")
        || self.bump_if("?<!")
    }

    /// Bump the parser, and if the `x` flag is enabled, bump through any
    /// subsequent spaces. Return true if and only if the parser is not at