[Proposal]: Support combination of literal and union types

[QsROg8320]

It will be good if c# supports a combination of literal and union types like typescript. So ultimately, I want to be able to write like that:

type Color: string { "Red" | "Black" | "White"}
type SomeNumber: int { 2..99 | 101}

void CombineColors(Color colorA,Color colorB){}
CombineColors("Red","Black"); //OK
CombineColors("Yellow","Orange"); //Error

void Calc(SomeNumber number){}
Calc(5); //OK
Calc(202); //Error

[svick]

I think this should be achievable with an analyzer and some implicit conversions.