Two-phase lookup requires this to be interpreted at template parse time as two comparisons and a comma operator, because a, b and c are dependent names (which,

Two-phase lookup requires this to be interpreted at template parse time as two comparisons and a comma operator, because a, b and c are dependent names (which, without further disambiguation with the typename or template keyword, are taken to be variables). This has been the case since the first ISO C++ standard (published in 1998).