Constant UNSATISFIABLE_DIAGNOSTIC_CODE 

pub const UNSATISFIABLE_DIAGNOSTIC_CODE: &str = "unsatisfiable-requirement";

Stable [Diagnostic::code] set on the unsatisfiable-requirement diagnostic.

Set by generate_diagnostics_from_cache, so build_unsatisfiable_fix_action’s stashed CodeAction::data can name it and the deps-lsp handler’s diagnostic-binding step can match on it — the same mechanism build_vulnerability_fix_action uses with an advisory id, generalized to a constant since this diagnostic has no per-instance identifier.