<===> input.scss
// line-endings in this file must be CRLF
@import url("foo\
bar");
@import url("foo
bar");
@import url(foo
bar);

<===> error-dart-sass
Error: Expected ".
  ,
4 | @import url("foo
  |                 ^
  '
  input.scss 4:17  root stylesheet

<===> output.css
@import url("foobar");
@import url("foo\a bar");
@import url(foo bar);

<===> warning
DEPRECATION WARNING on line 4, column 13 of input.scss:
Unescaped multiline strings are deprecated and will be removed in a future version of Sass.
To include a newline in a string, use "\a" or "\a " as in CSS.