diagnostics

Shared diagnostic types for parser/validator/CLI.

Code generation

Diagnostic ID constants (codes::ARITY, etc.) and the explain() function are auto-generated from spec/diagnostics.jsonc at build time via build.rs. This makes the JSONC file the single source of truth — adding or updating a diagnostic only requires editing the spec, and the Rust code regenerates automatically.

Types

• Span { start: usize, end: usize } -- canonical byte-offset span, re-exported by core::grammar::diag.
• Severity: Error | Warn | Info. Implements Display (lowercase: error, warn, info).
• Diagnostic { id, severity, message, span, context } with convenience constructors: Diagnostic::error(), ::warn(), ::info().
  • context: Option<BTreeMap<String, String>> — machine-readable structured metadata for tooling. Uses BTreeMap for deterministic key ordering in JSON output. Attach via the .with_context(map) builder method. Omitted from serialized JSON when None.
  • Implements Display — formats as severity[id]: message (e.g. error[ZPL1101]: too many arguments).
  • Derives PartialEq, Eq for easy test assertions and exhaustive equality checks.

Functions

• explain(code: &str) -> Option<&'static str> -- human-readable explanation for all 45 diagnostic codes (auto-generated).
• Diagnostic::explain(&self) -> Option<&'static str> -- convenience method that calls the free explain() function with the diagnostic's own id.

Guidance

• Use stable IDs: ZPL1xxx (value-level), ZPL2xxx (structural/semantic), ZPL3xxx (notes), ZPL.PARSER.xxxx (parser).
• Keep messages concise and actionable.
• To add a new diagnostic: add an entry to spec/diagnostics.jsonc (in this crate) with id, constName, severity, category, summary, description, and contextKeys.
• See docs/DIAGNOSTIC_CODES.md for the full reference.