anchor.diff:  
   importDeclaration  
       : 'import' importPath ('.' wildcard | alias)? ';'
  -    -> ^(IMPORT_DECL ^(TYPE_NAME importElement*) wildcard? alias?)
  +    -> ^(IMPORT_DECL importPath wildcard? alias?)
       ;
       
   importPath
  
positive.code: grammar ceylon;
  
  options {
      //backtrack=true;
  
negative.code:     ;
  
  annotation
      : declarationModifier -> ^(ANNOTATION declarationModifier) 
      | userAnnotation
      ;
  
  //TODO: we could minimize backtracking by limiting the 
  