function tagCloseStart(code) {
    if (asciiAlpha(code)) {
      assert(code !== null) // Always the case.
      effects.consume(code)
      buffer = String.fromCharCode(code)
      return tagName
    }

    return nok(code)
  }
After `</`, in closing tag, at tag name.

```markdown
> | </x>
      ^
```

@type {State}