docs/reference/fidl/language/error-catalog/_fi-0058.md

## fi-0058: Reference to compiler generated payload name {:#fi-0058}

Anonymous method payloads have their names automatically generated by the FIDL
compiler, so that users of generated backend code may refer to the types they
represent as necessary. Referring to these types in *.fidl files themselves,
however, is forbidden:

{% include "docs/reference/fidl/language/error-catalog/label/_bad.md" %}

```fidl
{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/bad/fi-0058.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}
```

If you wish to refer to the payload type directly, you should extract the
payload type into its own named type declaration instead:

{% include "docs/reference/fidl/language/error-catalog/label/_good.md" %}

```fidl
{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/good/fi-0058.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}
```

All FIDL methods and events reserve the `[PROTOCOL_NAME][METHOD_NAME]Request`
name for their anonymous request payloads. Infallible two-way methods
additionally reserve `[PROTOCOL_NAME][METHOD_NAME]Response`. Fallible
two-methods reserve `[PROTOCOL_NAME][METHOD_NAME]TopResponse` instead.

<!-- TODO(fxbug.dev/109789): Remove last sentence once TopResponse is gone. -->