node_modules/eslint-plugin-lit/docs/rules/no-template-arrow.md

# Disallows arrow functions in templates (no-template-arrow)

Passing inline functions into templates will result in them
being created every time a render occurs, resulting in performance
loss.

Instead, you should do something like so:

```ts
_render() {
  return html`<x-foo @event=${this._onClick}>`;
}

_onClick() { ... }
```

As lit will automatically bind it to the correct context.

## Rule Details

This rule disallows using inline functions in templates.

The following patterns are considered warnings:

```ts
html`<x-foo @event=${() => {}}>`;
html`<x-foo @event=${function() { }}>`;
```

The following patterns are not warnings:

```ts
html`foo ${someVar}`;
```

## When Not To Use It

If you don't care about rendering performance, then you will not need this rule.