[]Constant rustc::util::ppaux::HIGHLIGHT_REGION

const HIGHLIGHT_REGION: LocalKey<Cell<Option<(RegionVid, usize)>>>
🔬 This is a nightly-only experimental API. (rustc_private)

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Mechanism for highlighting of specific regions for display in NLL region inference errors. Contains region to highlight and counter for number to use when highlighting.