docs/reference/fidl/language/error-catalog/_fi-0001.md

## fi-0001: Invalid character {:#fi-0001}

The lexer failed to convert a character into a token at
the specified location.

{% 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-0001.noformat.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}
```

An invalid character should be fixed by substitution or removal.

{% 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-0001.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}
```

Invalid characters are location dependent. Please refer to the
[FIDL language specification](/docs/reference/fidl/language/language.md) to determine
which characters are permitted in each part of the FIDL syntax.