trace.StartRegion(ctx, "unended region")

		trace.WithRegion(ctx, "region0", func() {
			// EvUserRegionBegin("region0", start)
			trace.WithRegion(ctx, "region1", func() {
				trace.Log(ctx, "key0", "0123456789abcdef") // EvUserLog("task0", "key0", "0....f")
			})
			// EvUserRegionEnd("region0", end)
		})
	}()
	wg.Wait()

	preExistingRegion.End()
	postExistingRegion := trace.StartRegion(bgctx, "post-existing region")

	EvUserTaskEnd       = 46 // end of task [timestamp, internal task id, stack]
	EvUserRegion        = 47 // trace.WithRegion [timestamp, internal task id, mode(0:start, 1:end), name string, stack]
	EvUserLog           = 48 // trace.Log [timestamp, internal id, key string id, stack, value string]
	EvCPUSample         = 49 // CPU profiling sample [timestamp, real timestamp, real P id (-1 when absent), goroutine id, stack]

	EvUserRegionBegin // trace.{Start,With}Region [timestamp, internal task ID, name string ID, stack ID]
	EvUserRegionEnd   // trace.{End,With}Region [timestamp, internal task ID, name string ID, stack ID]
	EvUserLog         // trace.Log [timestamp, internal task ID, key string ID, value string ID, stack]

	// Coroutines. Added in Go 1.23.
	EvGoSwitch        // goroutine switch (coroswitch) [timestamp, goroutine ID, goroutine seq]

			mappedType = go122.EvUserRegionBegin
		case 1: // end
			mappedType = go122.EvUserRegionEnd
		}
		mappedArgs = timedEventArgs{ev.Args[0], ev.Args[2], uint64(ev.StkID)}
	case oldtrace.EvUserLog:
		mappedType = go122.EvUserLog
		mappedArgs = timedEventArgs{ev.Args[0], ev.Args[1], it.inlineToStringID[ev.Args[3]], uint64(ev.StkID)}
	case oldtrace.EvCPUSample:
		mappedType = go122.EvCPUSample

					ev.args = append(ev.args, v)
				}
			} else {
				// Skip over arguments
				if !p.discard(v) {
					return fmt.Errorf("failed to read trace: %w", io.EOF)
				}
			}
			if typ == EvUserLog {
				// EvUserLog records are followed by a value string
				if flags&skipArgs == 0 {
					// Read string
					s, err := p.readStr()
					if err != nil {
						return err
					}
					ev.sargs = append(ev.sargs, s)

}

// Log returns details about a Log event.
//
// Panics if Kind != EventLog.
func (e Event) Log() Log {
	if e.Kind() != EventLog {
		panic("Log called on non-Log event")
	}
	if e.base.typ != go122.EvUserLog {
		panic(fmt.Sprintf("internal error: unexpected event type for Log kind: %s", go122.EventString(e.base.typ)))
	}
	return Log{
		Task:     TaskID(e.base.args[0]),

	go122.EvUserTaskEnd:     (*ordering).advanceUserTaskEnd,
	go122.EvUserRegionBegin: (*ordering).advanceUserRegionBegin,
	go122.EvUserRegionEnd:   (*ordering).advanceUserRegionEnd,
	go122.EvUserLog:         (*ordering).advanceAnnotation,

	// Coroutines. Added in Go 1.23.
	go122.EvGoSwitch:        (*ordering).advanceGoSwitch,
	go122.EvGoSwitchDestroy: (*ordering).advanceGoSwitch,