"Compiler diagnostics and Rust codegen ergonomics"

Compiler diagnostics and Rust codegen ergonomics

Diagnostics: miette vs custom errors

Current state:

  • miette is a dependency of vox-compiler and is used for Rust codegen failures (codegen_rust/pipeline.rs, emit/mod.rs, projection validation).
  • Parse / typecheck / HIR use bespoke error types (ParseError, Diagnostic, HirValidationError) mapped to LSP in vox-lsp.

Decision (near term):

  • No forced unification until there is bandwidth to thread Span ↔ miette::SourceSpan (including UTF-16 LSP offsets) through the full pipeline.
  • Directional preference: when adding new rich user-facing errors in codegen paths, use miette. For LSP-facing parse/type errors, keep the existing structured diagnostics until a deliberate migration plan exists.

Rationale: Unifying on miette everywhere is high-touch (CLI, MCP, tests, serde-stable diagnostics); partial adoption already delivers value on codegen.

Rust emission: quote / prettyplease

Current state: Most Rust output is string emission under crates/vox-compiler/src/codegen_rust/emit/.

Decision:

  • Pilot first: pick one hot file (e.g. a small emit/* module with heavy escaping) and try quote! for syntactic fragments; optionally run prettyplease on output in tests only to validate shape.
  • Not a goal: rewriting the entire emitter to proc-macro style in one pass.

Rationale: quote reduces nested-quote bugs; full migration is a large formatting and snapshot-test churn.

References

  • crates/vox-compiler/src/codegen_rust/pipeline.rs
  • crates/vox-compiler/src/parser/error.rs
  • crates/vox-compiler/src/typeck/diagnostics.rs
  • crates/vox-lsp/src/lib.rs (diagnostic mapping)