docs/reference/fidl/language/error-catalog/_fi-0090.md

## fi-0090: Duplicate canonical struct member name {:#fi-0090}

Canonical struct member names cannot be repeated:

{% 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-0090.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}
```

Even though `myStructMember` and `MyStructMember` look different, they are both
represented by the **canonical** name `my_struct_member`. You get the canonical
name by converting the original name to `snake_case`.

To fix the error, give each member a name that is unique after canonicalization:

{% 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-0090.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}
```

See [fi-0035](#fi-0035) for more details on why FIDL requires declarations to
have unique canonical names.