I just updated to the latest nightly, which is the first 1.31 release I install.
old: rustc 1.30.0-nightly (63d51e89a 2018-09-28)
new: rustc 1.31.0-nightly (5597ee8a6 2018-10-03)
For the new version, I can install neither the rls-preview nor the clippy-preview component. Is this expected? And is there any workaround, short of downgrading to the old nightly?
Still there for me in rustc 1.31.0-nightly (8c4ad4e9e 2018-10-04).
Maybe it was a bad build but I thought now they were strict requirements for the build. (In past was no link to a build compiling with either.)
Not for nightly anymore, just beta. If you use rustup update nightly it will avoid updating to a version that is lacking any of the components you have installed, but I don't know of any way to update your nightly channel to the latest version containing the tools you need.
Yeah, it actually did prevent me from updating, with an error indicating that it could not download the components. I thought maybe the components have been renamed ("rls" instead of "rls-preview" or whatever), so I removed them, upgraded, and then tried to reinstall them, but they were gone.
In the 2018-10-04 version they are back, so all good now, and next time I will know better.