The error is in MulExp::semantic. It happens no matter if the multiplication expression is in a template. These are the combinations that fail:

IF / ifloat
IF / IF
ID / idouble
ID / ID
IR / ireal
IR / IR


Here's a sample:

import std.stdio;

typedef ifloat IF;
typedef idouble ID;
typedef ireal IR;

template PrintAddedType(X, Y)
{
	void PrintAddedType()
	{
		X x;
		Y y;
		writeln( typeid( x ), " ", typeid( y ), " ", typeid( x / y ) );
	}
}

template PrintAddedType(X)
{
	void PrintAddedType()
	{
/*
		PrintAddedType!(X, ifloat)();
		PrintAddedType!(X, idouble)();
		PrintAddedType!(X, ireal)();
*/
/*
		PrintAddedType!(X, IF)();
		PrintAddedType!(X, ID)();
		PrintAddedType!(X, IR)();
*/
	}
}

void main()
{
/*
	PrintAddedType!(IF)();
	PrintAddedType!(ID)();
	PrintAddedType!(IR)();
*/
	IR x;
	IR y;
	writeln( typeid( x ), " ", typeid( y ), " ", typeid( x / y ) );
}