In other words, the proposal is more-or-less that C++ should introduce a new token, ::< , which is treated by the parser as "The same token as < but it's invariably an angle bracket, not a less-than sign." Phrased that way, the proposal is
.
I would like to see some kind of cleanup around angle-brackets, but this particular small fix doesn't provide enough benefit to justify its cost.
The cost of changing the parser is honestly not very big (we did it for operator<=>). But our changes should find ways to improve the code people already write, like
template<enable_if_t<X,int>=0> // syntax error because ">=" is a token
The proposed change merely takes code that people already avoid (because it is ugly) and introduces a special-case ad-hoc hack to make it still ugly but 7 characters shorter. Which nobody will use, because in order to use it you have to know that the problem exists, and once you know the problem exists, the problem is already solved. The problems we should focus on solving are the problems that people tend to run into without understanding them.
I don't like "Down with typename!" either, but at least it was focused on making the compiler accept the code that people already write. This proposal just makes up a new syntax that people won't want to write (even if they knew they could, which they won't).
I'm even more confident that it fixes
using f = T::type<0>;
because that is a typeid-only context, where the `<` cannot possibly denote a less-than sign.
my $.02,
–Arthur