vscode invalid syntax error for dart and flutter after pressing the Ctrl+Shift+I short to format the code in readable form

I am using vscode in ubuntu for developing flutter application. I installed the flutter and dart extension for vscode. when I write code and keep it the same dirty format it doesn't take any syntax error -although it shouldn't- but after I reformat the code in a readable shape using Ctrl+Shift+i short-key vscode takes syntax error. However, when I close the file (here the .dart file) and re-open it, all errors is gone. You can see it more in the picture. I don't know how to handle this kinda error.