117 effect resume produce is call

// Produce-is-the-call: an effect arm resumes with the single payload produced
// by calling a bare-return event. `->` is the produce glyph; its RHS may be an
// event call (`mix(x: p)`), so the resume value flows straight from a nested
// single-payload event — no intermediate `: bind`. The emitter binds the call
// to a temp and returns it (`const r = mix-handler(...); return r;`), where
// `mix` is itself a `-> T` bare return (plain payload, no tagged union).
//
// This is the hot-path shape the bare_return microbench needs: a single-payload
// event invoked once per effect firing, its output threaded as the resume.
~import std/io

~pub event mix { x: i32 } -> i32
~proc mix|zig { return x + 1; }

~pub event driver {}
! step i32 -> i32
| done i32

~proc driver|zig {
    return .{ .done = step(41) };
}

~driver()
! step p -> mix(x: p)
| done r |> std/io:print.ln("{{ r:d }}")