Multi-shot effect is not supported on the native backend

Why this fires¶

A perform targets an effect operation declared multi (resumable more than once — a multi-shot continuation):

effect Choice { multi fn pick(opts: [int]) -> int }

The native (Cranelift) backend's calling convention has no support for stack-copying continuations, so a multi-shot effect operation can only run on the VM. The effect-safety pass has a native-backend mode (EffectBackend::Native) that rejects performs of multi operations for exactly this reason.

Current status: as of this writing, zolo build --target native does not actually run the effect-safety pass in its native-backend mode — a program using multi fn builds and runs natively today without TE812 ever firing (the multi-shot semantics simply aren't exercised by the test program in that case). TE812 is reachable through the compiler's internal API (zolo_compiler::compiler::compile_to_lua_with_native_effect_check), which is how the compiler's own test suite exercises it; it is not yet wired into the zolo build --target native CLI path.

Fix it¶

• Run the program on the VM (zolo run file.zolo), which fully supports multi-shot effects.
• If native/LLVM support is required, avoid multi-shot operations — restructure the effect to only resume once (or not at all), which both backends support.

See also¶

• /docs/algebraic-effects — effect operations and multi-shot handlers.