SassのSASS記法だとマップ変数のところでエラーが出る。
検索してもほとんど出てこなかったのでここにメモ書きしておく

@use "sass:map"

// 以下の書き方だとOK
$breakpoint-up: ("sm": "only screen and (min-width: 400px)","md": "print, screen and (min-width: 768px)","lg": "print, screen and (min-width: 980px)","xl": "print, screen and (min-width: 1400px)",) !default 
// 以下の書き方だとエラーが出る
$breakpoint-up: (
  "sm": "only screen and (min-width: 400px)",
  "md": "print, screen and (min-width: 768px)",
  "lg": "print, screen and (min-width: 980px)",
  "xl": "print, screen and (min-width: 1400px)",
) !default

SASS記法の場合、map変数は一行で書く必要がある
うっかり忘れるけど@use "sass:map"も必要