For enums, the constructor gives an alternative place to put generic arguments. E. g. you can write None::<T> or Option::None::<T> instead of Option::<T>::None. I suppose for a full “importing trait/type methods” feature, one might need a way to still be able to specify the generic arguments of the type, or the generic arguments and/or Self type of the trait, I suppose? Or maybe not...? If yes, it's less straightforward than with enum constructors, because methods can also already have some generic arguments for themselves. If I can import String::new, can I also import String::default, too, or only the more generic Default::default? Maybe I can even import Foo::<Bar>::baz for a specific instantiation (with Bar) of the generic argument(s)? All of this opens a lot of design space that someone would have to address, discuss, and propose best solutions for, before such a feature could be introduced and stabilized.
1 Like