anchor.diff:      return _node(search, (n) => n is ListLiteral);
     }
   
  -  MapLiteral mapLiteral(String search) {
  -    return _node(search, (n) => n is MapLiteral);
  +  SetOrMapLiteral mapLiteral(String search) {
  +    return _node(search, (n) => n is SetOrMapLiteral && n.isMap);
     }
   
     MethodDeclaration methodDeclaration(String search) {
  
positive.code:     return _node(search, (n) => n is FieldFormalParameter);
    }
  
    ForEachStatement forEachStatement(String search) {
      return _node(search, (n) => n is ForEachStatement);
    }
  
    ForStatement forStatement(String search) {
      return _node(search, (n) => n is ForStatement);
    }
  
    FunctionBody functionBody(String search) {
  
negative.code:     return _node(search, (n) => n is RethrowExpression);
    }
  
    SetOrMapLiteral setLiteral(String search) {
      return _node(search, (n) => n is SetOrMapLiteral && n.isSet);
    }
  
    SetOrMapLiteral setOrMapLiteral(String search) {
  