file_names
The file name '{0}' isn't a lower_case_with_underscores identifier.
Description
#The analyzer produces this diagnostic when the name of a .dart file
doesn't use lower_case_with_underscores.
Example
#A file named SliderMenu.dart produces this diagnostic because the file
name uses the UpperCamelCase convention.
Common fixes
#Rename the file to use the lower_case_with_underscores convention, such as
slider_menu.dart.