Comparing two AliasSeq

[Yuxuan Shui via Digitalmars-d-learn]

In this example:

     import std.range;
     template expandRange(alias R) if (isInputRange!(typeof(R))) {
         static if (R.empty)
	    alias expandRange = AliasSeq!();
         else
	    alias expandRange = AliasSeq!(R.front(), 
expandRange!(R.drop(1)));
     }

     ///
     unittest {
         import std.range;
         static assert (is(expandRange!(iota(0,5)): 
AliasSeq!(0,1,2,3,4)));
     }

The static assert fails, why?