Rollup merge of #133159 - Zalathar:unstable-options-no-value, r=jieyouxu

Don't allow `-Zunstable-options` to take a value

Passing an explicit boolean value (`-Zunstable-options=on`, `off` etc.) sometimes appears to work, but actually puts the compiler into an unintended state where unstable _options_ are still forbidden, but unstable values of _some_ stable options are allowed.

This is a result of `-Zunstable-options` being checked in multiple different places, in slightly different ways. Fixing the checks in `config::nightly_options` to understand boolean values would be non-trivial, so for now it's easier to make things consistent by forbidding values in the `-Z` parser.

---

There were a few uses of this in tests, which happened to work because they were tests of unstable values.

0 files changed, 0 insertions, 0 deletions