anchor.diff:  
       rule argspec:       argspec_item                {{ v = [argspec_item] }}
                           (
  -                            COMMA
  +                            ","
                               argspec_item            {{ v.append(argspec_item) }}
                           )*                          {{ return ArgspecLiteral(v) }}
   
  -    rule argspec_item:  (
  -                            KWVAR ":" expr_slst     {{ return (KWVAR, expr_slst) }}
  -                            | expr_slst             {{ return (None, expr_slst) }}
  -                        )
  +    rule argspec_item:
  +                        KWVAR ":" expr_slst         {{ return (KWVAR, expr_slst) }}
  +                        | expr_slst                 {{ return (None, expr_slst) }}
   
       rule expr_lst:      expr_slst                   {{ v = [expr_slst] }}
                           (
  -                            COMMA
  +                            ","
                               expr_slst               {{ v.append(expr_slst) }}
                           )*                          {{ return ListLiteral(v) if len(v) > 1 else v[0] }}
   
  
positive.code: %%
  parser SassExpression:
      ignore: "[ \r\t\n]+"
      token COMMA: ","
      token LPAR: "\\(|\\["
      token RPAR: "\\)|\\]"
      token END: "$"
  
negative.code:     token UNITS: "(?<!\s)(?:[a-zA-Z]+|%)(?![-\w])"
      token NUM: "(?:\d+(?:\.\d*)?|\.\d+)"
      token COLOR: "#(?:[a-fA-F0-9]{6}|[a-fA-F0-9]{3})(?![a-fA-F0-9])"
      token KWVAR: "\$[-a-zA-Z0-9_]+(?=\s*:)"
      token VAR: "\$[-a-zA-Z0-9_]+"
      token FNCT: "[-a-zA-Z_][-a-zA-Z0-9_]*(?=\()"
      token ID: "[-a-zA-Z_][-a-zA-Z0-9_]*"
  