It would be useful to use the tag part of a tagged union on its own, and it would fit in well with the rest of std.variant.

It's not always the case that you want to store actual data, sometimes you just need to store the type. Also sometimes you need to store the data somewhere else or store it in such a way that you can specify the type first and fill in the data later.

eg.
	alias TypeEnum!(
		void,
		byte,
		short,
		string,
		Object
	) TestTypeEnum;
	
	TestTypeEnum test;
	
	assert(test == TestTypeEnum.from!void);
	assert(test != TestTypeEnum.from!byte);
	
	test = TestTypeEnum.from!string;
	
	assert(test == TestTypeEnum.from!string);
	assert(test != TestTypeEnum.from!Object);
	
	static assert(!__traits(compiles, TestTypeEnum.from!float));

(pull request shortly)