---
title: 'CHR0054: Reactor method has an unsupported return type'
editUrl: https://github.com/Cratis/Chronicle/edit/main/Documentation/code-analysis/CHR0054.mdx
description: CHR0054 reports a reactor handler return type that Chronicle does not discover.
---


## Rule description

A reactor method whose first parameter is an `[EventType]` but whose synchronous return type is not one of the supported shapes is skipped during handler discovery. CHR0054 reports that return type, rather than treating it as an unresolvable parameter.

## Severity

Warning

## Supported returns

- `void` or `Task`.
- A registered event type, `EventForEventSourceId`, or `EventsWithConcurrencyScopes`.
- `IEnumerable<T>` where `T` is a registered event type, `EventForEventSourceId`, or `object` (for mixed events and targeted events).
- `Task<T>` for any side effect that a registered reactor side-effect handler can process, including the shapes above.

A synchronous custom side-effect type cannot be discovered as a reactor handler. Return it from `Task<T>` instead and register an `IReactorSideEffectHandler` that can handle its value.

## Related rules

- [CHR0004](/chronicle/code-analysis/chr0004/): Reactor method has a parameter that cannot be resolved.
- [CHR0005](/chronicle/code-analysis/chr0005/): Reactor event parameter must have `[EventType]` attribute.