Add support for semantic token enumMember declaration modifier

Feature Request

Right now, enums have the semantic token type enumMember but without modifiers. I'd like to distinguish between declaration and usage.

In my color theme, I have opted to use a green color for constants. I'd like it so that I could make enum usage be green but usage only. Not the enum declaration/definition.

This is what's currently possible:

I can apply my green color to the enumMember sematic token.

However, that makes the enum definition also green which I don't want. Here you can see that green is applied on both sides of the equals sign.

I'd like this to stay like this

But there's no way to accomplish this without a semantic token modifier. I've tried TextMate scope mappings and contribution points to as a workaround but it's not possible and I cannot disable semantic highlighting because it will just lead to other issues. The semantic highlighting rules takes precedence.

I would really appreciate if we could get a declaration modifier for enums, so that I can have my enum declaration appear in a my natural foreground color but when used as a literal constant value, use my green color.

Start by tracing how the extension produces enumMember semantic tokens and how declaration-versus-usage information is represented. Done means enum declarations can receive a declaration modifier while enum usages remain distinguishable for theme coloring, without disabling semantic highlighting.