Weird "circular initialization of isInputRange" error

[Alex Parrill via Digitalmars-d]

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