tap on bare return

// Test 508: Tap observing a bare-return (`-> T`) event.
//
// A bare-return event has no named branch, so the branch-name tap body
// (`| result |> ...`) has nothing to match. Instead the tap binds the
// produced value with `:` — the exact call-site bind rule as
// `~compute(...): v |> ...`. Design ruled by Lars 2026-06-25.

const std = @import("std");
~import std/taps
~import std/io

~event compute { x: i32 } -> i32

~proc compute|zig {
    std.debug.print("compute({d})\n", .{x});
    return x * 2;
}

~event observed { value: i32 }

~proc observed|zig {
    std.debug.print("[TAP] saw {d}\n", .{value});
}

// Observe compute's bare-return production; bind the produced value as `v`.
~tap(compute -> *): v |> observed(value: v)

// Main flow that triggers the tap.
~compute(x: 21): r |> std/io:print.ln("main: {{ r:d }}")