This piece of code (which I reduced with dustmite) gives me the following error when I try to compile it:

> $ rdmd -main parser.d parser.d(28): Error: circular initialization of isInputRange
> parser.d(31): Error: template instance std.meta.staticMap!(handler, ArrayReader*) error instantiating
> parser.d(36):        instantiated from here: unpacker!(RefRange!(immutable(ubyte)[]))
> parser.d(40): Error: template instance std.range.primitives.isInputRange!(ArrayReader*) error instantiating
> /usr/include/dmd/phobos/std/meta.d(546):        instantiated from here: F!(ArrayReader*)
> parser.d(43):        instantiated from here: staticMap!(toTD, ArrayReader*)
> Failed: ["dmd", "-main", "-v", "-o-", "parser.d", "-I."]

I'm not really sure what's causing the error; I'm not declaring `isInputRange` in my code. Commenting out the definition of `TD` (the very last line) removes the error. Am I doing something wrong here, or is this a compiler bug?

Tested with dmd v2.068.1 on Linux x64

Code:
-----
> import std.range;
> import std.variant;
> import std.typetuple;
> 
> ///
> template unpacker(Range)
> {
> 	/// Element data types. See `unpack` for usage.
> 	alias MsgPackData = Algebraic!(
> 		ArrayReader*,
> 	);
> 
> 	
> 	/// Reader range for arrays.
> 	struct ArrayReader {
> 		MsgPackData _front;
> 		void update() {
> 			_front.drain;
> 		}
> 		
> 		void popFront() {
> 			update;
> 		}
> 	}
> 	
> 	void drain(MsgPackData d) {
> 		static handler(T)(T t) {
> 			static if(isInputRange!T)
> 				data;
> 		}
> 		d.visit!(staticMap!(handler, MsgPackData.AllowedTypes));
> 	}
> }
> 
> 
> alias TestUnpacker = unpacker!(RefRange!(immutable(ubyte)[]));
> alias D = TestUnpacker.MsgPackData;
> 
> template toTD(T) {
> 	static if(isInputRange!T)
> 		alias toTD = This;
> }
> alias TD = Algebraic!(staticMap!(toTD, D.AllowedTypes)); // test data type