docs/reference/fidl/language/error-catalog/_fi-0035.md

## fi-0035: Canonical name collision {:#fi-0035}

Two declarations cannot have the same canonical name:

{% 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-0035.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}
```

Even though `COLOR` and `Color` look different, they are both represented by the
**canonical** name `color`. You get the canonical name by converting the
original name to `snake_case`.

To fix the error, give each declaration 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-0035.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}
```

Following the [FIDL style guide][fidl-style-naming]'s naming guidelines will
minimize your chances of running into this error. Canonical name collisions will
never happen between declarations that use the same casing style, and they will
rarely happen between ones that use different styles because of other
requirements (e.g. protocol names should usually be noun phrases ending in -er).

FIDL enforces this rule because bindings generators transform names to the
idiomatic naming style for the target language. By ensuring unique canonical
names, we guarantee that bindings can do this without producing name collisions.
See [RFC-0040: Identifier uniqueness][RFC-0040] for more details.

[fidl-style-naming]: /docs/development/languages/fidl/guides/style.md#names
[RFC-0040]: /docs/contribute/governance/rfcs/0040_identifier_uniqueness.md