p.cindex++
		if list := c.List; len(list) > 0 {
			p.comment = c
			p.commentOffset = p.posFor(list[0].Pos()).Offset
			p.commentNewline = p.commentsHaveNewline(list)
			return
		}
		// we should not reach here (correct ASTs don't have empty
		// ast.CommentGroup nodes), but be conservative and try again
	}
	// no more comments
	p.commentOffset = infinity
}

	p.cindex = 0
	// don't overwrite any pending comment in the p.comment cache
	// (there may be a pending comment when a line comment is
	// immediately followed by a lead comment with no other
	// tokens between)
	if p.commentOffset == infinity {
		p.nextComment() // get comment ready for use
	}
}

type exprListMode uint

const (
	commaTerm exprListMode = 1 << iota // list is optionally terminated by a comma