It's interesting that HN zapped the second colon. The headline here (at time of my posting) is:

"Identifying Rust's collect:<Vec<_>>() memory leak footgun"

but the actual title of the blog post is:

"Identifying Rust's collect::<Vec<_>>() memory leak footgun"

That extra colon matters to Rust's syntax.

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

Yes? What about unamused Vec?