According to spec, the syntax tells us that you're able to use space separated values. So fallback to string is necessary. But a goal I have is that display won't do that so I'm currently experimenting of combining data types with keywords to prevent that. So the result will be like: 'block' | 'flow' | 'block flow' | 'flow block' | ...

Ah, I never knew display supported multiple values.

I was about to post the same issue for alignItems and justifyContent. I take it these need to support multiple values too?

Exposing an AlignItemsSingle type would be useful for disabling multiple values in certain contexts where you're sure you don't need it. E.g.:

export type AlignItemsSingleProperty = Globals | SelfPosition | "baseline" | "normal" | "stretch";
export type AlignItemsProperty = AlignItemsSingleProperty | string;

I've started working on combined keywords #22 but halted partly due to #51. I'm afraid that it may have impact on performance if unions increase to an unsustainable amount. I could however limit that some how if that becomes a problem.

Too many type aliases seems to have an impact on performance too. So I'm a bit conservative to splitting them up.

I'll try to resume my work on combined keywords. To at least try it out. But I haven't come that far so anyone is welcome to submit a PR.

Fixed in #74