Summary

Only State<T> effect handlers compile to WASM. Exn<E> and custom effect handlers are not yet supported in codegen.

Current state

• handle[State<T>] compiles via host imports (vera.state_get, vera.state_put)
• Functions containing handle[Exn<E>] or custom handlers are skipped with a warning
• The type checker and verifier handle all effect types correctly
• Only codegen is limited to State

What's needed

• Exn<E> handler compilation (non-resuming handlers / exception semantics)
• Custom effect handler compilation (general one-shot continuations)
• Multi-shot continuations for effects like Choice (advanced)
• WASM exception handling proposal integration (for Exn)

Spec reference

Chapter 11, Sections 11.11.4 and 11.12 "Limitations"