"No matching toolchain" for nightly channel in 0.57.1

[the80srobot]

When upgrading from rules_rust 0.54.1 to 0.57.1, I noticed that the rust toolchain can no longer be set to the nightly channel, because there are "no matching toolchains". (This is on Bazel 8.0.0)

This works:

rust.toolchain(
    edition = "2021",
    versions = ["1.84.1"],
)

This doesn't:

rust.toolchain(
    edition = "2021",
    versions = ["nightly/2025-01-30"]
)

Or, indeed other ISO dates that used to work.

You get this error:

ERROR: /home/debian/pedro/rednose/BUILD:24:20: While resolving toolchains for target //rednose:rednose (ce83c71): No matching toolchains found for types @@rules_rust+//rust:toolchain_type.
To debug, rerun with --toolchain_resolution_debug='@@rules_rust+//rust:toolchain_type'
For more information on platforms or toolchains see https://bazel.build/concepts/platforms-intro.
ERROR: Analysis of target '//rednose:rednose' failed; build aborted
INFO: Elapsed time: 0.310s, Critical Path: 0.00s
INFO: 1 process: 1 internal.
ERROR: Build did NOT complete successfully