Method check

regex/regex-syntax/src/ast/parse.rs:2126–2128

(self, ast: &Ast)

    }

    fn check(self, ast: &Ast) -> Result<()> {
        ast::visit(ast, self)
    }

    fn increment_depth(&mut self, span: &Span) -> Result<()> {
        let new = self.depth.checked_add(1).ok_or_else(|| self.p.error(