`-Zpolonius` help text says `(default: no)` on nightlies where the default is `next`

[connorshea]

On current nightly, Polonius is enabled by default (see also #160456), but -Z help still says the default is no.

$ rustc --version
rustc 1.100.0-nightly (c656540d6 2026-08-21)

$ rustc -Z help | grep polonius
    -Z    polonius=val -- enable polonius-based borrow-checker (default: no)

I expected to see this happen: the default is described as next in the help text because nightly enables Polonius by default.

Instead, this happened: the default is described as no in the help text.

I think this is because compiler/rustc_session/src/options.rs:2751 is a static string, and it should probably vary based on CFG_DEFAULT_POLONIUS_NEXT?

Meta

rustc --version --verbose:

rustc 1.100.0-nightly (c656540d6 2026-08-21)
binary: rustc
commit-hash: c656540d6467dee1381f0cbd882412d6bd1cd5ae
commit-date: 2026-08-21
host: aarch64-apple-darwin
release: 1.100.0-nightly
LLVM version: 23.1.0

Backtrace

N/A

AI Disclosure: Discovered while trying out the alpha borrow checker with an AI tool, then investigated with AI assistance. All commands and outputs above were run and verified manually by me, and the ticket contents were written by me.

[theemathas]

cc @jackh726