function contentBefore(code) {
    assert(markdownLineEnding(code), 'expected eol')
    effects.enter(types.lineEnding)
    effects.consume(code)
    effects.exit(types.lineEnding)
    return contentStart
  }
Before code content, not a closing fence, at eol.

```markdown
  | ~~~js
> | alert(1)
            ^
  | ~~~
```

@type {State}