camel_case_extensions

The extension name '{0}' isn't an UpperCamelCase identifier.

The analyzer produces this diagnostic when the name of an extension doesn't use the 'UpperCamelCase' naming convention.

The following code produces this diagnostic because the name of the extension doesn't start with an uppercase letter:

extension stringExtension on String {}

If the extension needs to have a name (needs to be visible outside this library), then rename the extension so that it has a valid name:

extension StringExtension on String {}

If the extension doesn't need to have a name, then remove the name of the extension:

extension on String {}