docs/reference/fidl/language/error-catalog/_fi-0158.md

## fi-0158: Cannot bound twice {:#fi-0158}

An `alias` declaration cannot change the value of an already set constraint on
the type it is aliasing:

{% 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-0158.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}
```

Instead, the unbounded definition should receive its own `alias` declaration,
and each further constrained alias should inherit from it in turn:

{% 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-0158.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}
```

This is disallowed to avoid confusion and compiler implementation complexity.