Feature request: std::fmt::Write::write_line

hexchat-plugin has a print(impl ToString) which is a line-writer. It doesn't support the equivalent of write_fmt. It'd be nice if write_fmt and write_line were separate so that our write_fmt could be unimplemented!() and write_line didn't push a newline at the end (altho hexchat doesn't care about a terminating newline, and in fact slightly prefers it, but w/e).

This would be used by writeln!.

You can use something like a LineBuffer that flushes on newlines to support such a writer.

std::fmt::Write is supposed to have a write_str but it'd be nice to have that be unimplemented!() and also have write_fmt be unimplemented!() and also have write_char be unimplemented!() and instead have write_line implemented.

this is the source code for the crate, consider taking a look at it: lib.rs - source we had an argument about this very issue on the community discord, also note that the default write_fmt calls write_str multiple times which is extremely less-than-ideal for this use-case and we're also not sure if there's any guarantee that write_fmt doesn't get called multiple times.