Not sure what you're asking. At risk of loosely explaining what you may already know, `<Vec<_>>` is a generic parameter `<T>` with the type `T` specified as `Vec`. Vec also has a param, `<_>`, where the type is ignored - as the compiler can figure that out.
Sidenote, `<Vec<_>>` is missing the best part - the fish head, to become `::<Vec<_>>`, aka `::<>` - the Turbo Fish :D
I admit to using this syntax more than necessary just so i can write a turbofish :D
edit: Wait no, `<>` is the head - isn't it. hah. So i guess it's missing the fins? /shrug
Sidenote, `<Vec<_>>` is missing the best part - the fish head, to become `::<Vec<_>>`, aka `::<>` - the Turbo Fish :D
I admit to using this syntax more than necessary just so i can write a turbofish :D
edit: Wait no, `<>` is the head - isn't it. hah. So i guess it's missing the fins? /shrug