# RAN010 Owned node created in a pure derivation

`error RAN010`: *`createEffect` creates an owned node inside `createMemo`'s body, which fails every read of the memo.*

**Cause.** A memo, effect, async value, boundary, root, projection, lookup, selector or `onCleanup` created in a pure
derivation fails the derivation's run with `InvalidOperationException`: the body of `createMemo` or `Memo (graph,
compute)`, the compute of `createAsync` and `createEffectOn`, a projection's map or row reader, a lookup's `f` and
`affected`, an editable's seed, and a projection aggregate's functions. A creator under `untrack` or inside `try ...
with` fails the same way. A creator inside a nested lambda, other than `untrack` and `batch`, is not reported, even one
that runs immediately, such as `List.map`'s.

**Fix.** Use the owning form (`createMemoWith`, `createAsyncWith`), or create the node outside. The rule's fix renames
the memo and async creators.

### Triggers

```fsharp
module Example

open Ranvier

let label (topic: Signal<string>) =
    createMemo (fun _ ->
        onCleanup ignore
        topic.Value)
```

### Fixed

```fsharp
module Example

open Ranvier

let label (topic: Signal<string>) =
    createMemoWith (fun _ ->
        onCleanup ignore
        topic.Value)
```

**Suppression.** `// fsharpanalyzer: ignore-line RAN010`, with the reason on the line before.