fi-0160: Type cannot be marked as optional twice {:#fi-0160}

This error occurs when a type is made optional twice. Usually, this occurs when the type is marked optional at both its use and declaration sites.

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

{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/bad/fi-0160.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}

To fix this error, only make the type optional once.

For example, you can remove :optional from the use site.

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

{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/good/fi-0160-a.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}

You could also remove :optional from the alias declaration.

{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/good/fi-0160-b.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}