assignment

I had this mistype in my program, and was wondering why the blitz debugger never picks it up (debugging on and off).

res=a=hi()     ;the problem part
Function hi()
	Return 1
End Function
print res
print a
waitkey()
end

in fact, it won't even catch it if the line is simply res=a=5 or any other constant. Is this supposed to happen? If it is, shouldn't res also be assigned to the value?