<===> error/single_dot/input.scss
a {a: .}

<===> error/single_dot/error
Error: Expected digit.
  ,
1 | a {a: .}
  |        ^
  '
  input.scss 1:8  root stylesheet

<===> error/single_dot/error-libsass
Error: Invalid CSS after "a {a:": expected expression (e.g. 1px, bold), was ".}"