Vitte

Async Foundation (171)

Date: May 22, 2026

Objective

Prepare compiler/runtime integration for async execution.

Implemented Foundation

  • HIR lowering inspects items/statements/expressions for async/await markers.
  • Async intent is propagated at item level through lowered metadata markers.
  • Baseline misuse diagnosis:
  • HIRASYNC0001: await outside async procedure.

Contracts

  • await is only valid when procedure is async-marked.
  • Async markers survive lowering so MIR and later passes can branch behavior.
  • Non-async code paths remain unaffected.

Contract Diagnostics

  • Misuse is reported at HIR lowering stage as semantic error.
  • Diagnostic includes remediation note:
  • mark procedure async, or
  • remove await.

Follow-up Work

  • Dedicated async type (Future[T]) propagation in typeck.
  • Await lowering tied to explicit effect model.
  • Async borrow and lifetime diagnostics beyond baseline misuse detection.