For what is worth <- is already taken by the placement in syntax, which has been pulled back but rustc needs to continue parsing it to avoid breaking existing c

For what is worth <- is already taken by the placement in syntax, which has been pulled back but rustc needs to continue parsing it to avoid breaking existing code which used it behind cfg flags. It doesn't do anything but it has to be understood. It would be possible to resolve that problem, but it's another thing to be aware of.