Class names containing a verbatim (@) character cause the source generator to stop

[SteveDunn]

Describe the bug

When a class name has a verbatim character, it causes the source generator to stop

Steps to reproduce

[ValueObject]
public partial class @class { }

... produces:
warning CS8785: Generator 'ValueObjectGenerator' failed to generate source. It will not contribute to the output and compilation errors may occur as a result. Exception was of type 'ArgumentException' with message 'The hintName 'Whatever_@class.g.cs' contains an invalid character '@' at position 9.

Expected behaviour

For it to no stop the source generator.

It looks like the filename it chooses based on the class name is invalid.