# AUR0178

## Error Message

`AUR0178: Expression error: arrow function with function body is not supported: "{{expression}}"`

## Description

Aurelia binding expressions only support concise arrow function bodies (single expression). Block bodies (`{ ... }`) are not supported.

## Example Trigger

```html
<!-- ❌ Block body -->
<div textcontent.bind="x => { return x + 1; }"></div>
```

## Solution

* Use an expression body, or move logic to a view-model method.

```html
<!-- ✅ Expression body -->
<div textcontent.bind="x => x + 1"></div>
```