Comment this line at the start of the page

// ignore_for_file: prefer_const_constructors

Example:

What you probably want is just to remove only the blue lines and nothing else, then find the file pubspec.yaml and remove or comment the line with flutter_lints. Save and Make sure to restart the application.

Press command+shift+p (open command pallete)
Then type Disable Error Squiggles.
And click on that Disable Error Squiggles.

Rename Your file name to the login_page.dart.

This blue line shows the warning to us because of linter. There is a rule defined in the package that the file name must be lower_camel_case. This is because linter defines the bet practices.

remove flutter_lints: ^1.0.0 , its work for me. don't forget to pub get