Methods used by the deprecated C bindings cannot contain out of line data, so using union types therein is disallowed:
{% include “docs/reference/fidl/language/error-catalog/label/_bad.md” %}
{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/bad/fi-0137.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}
See fi-0138 for more details on why FIDL has special restrictions on types and protocols used by the C bindings.
