anchor.diff:    {KnownExtensions, UnknownExtensions} = group_extensions( tl(Parts) ),
   
     ReversedUnknownExtensions = if
  -    UnknownExtensions != [] ->
  +    UnknownExtensions /= [] ->
         UnknownExtensions = lists:reverse(UnknownExtensions);
       true -> []
     end,
  
positive.code: 
  
  compilers() ->
    [
      {"scss", wilcog_scss_compiler},
      {"js", wilcog_javascript_compiler},
      {"css", wilcog_css_compiler},
      {"coffee", wilcog_coffeescript_compiler},
    ].
  
  
  compiled_name_for(_SourceFilename, Basename, []) ->
    Basename.
  
  
  compiled_name_for(SourceFilename, Basename, KnownExtensions) ->
    Parts = [Basename] ++ [compute_extension(SourceFilename, lists:last(KnownExtensions))],
    string:join(Parts, ".").
  
negative.code: 
  
  compute_extension(SourceFilename, Extension) ->
    case is_valid_extension(Extension) of
      true ->
        Compiler = compiler_for(Extension),
        Compiler:expected_extension(SourceFilename);
      _ -> Extension
    end.
  
  is_valid_extension(Extension) ->
    compiler_for(Extension) and is_extension_defined(compiler_for(Extension)).
  
  
  is_extension_defined(Module)->
  