Method c_empty_look

regex/src/compile.rs:451–454

(&mut self, look: EmptyLook)

    }

    fn c_empty_look(&mut self, look: EmptyLook) -> Result {
        let hole = self.push_hole(InstHole::EmptyLook { look: look });
        Ok(Patch { hole: hole, entry: self.insts.len() - 1 })
    }

    fn c_concat<'a, I>(&mut self, exprs: I) -> Result
            where I: IntoIterator<Item=&'a Hir> {