# E3010

Only labelled arguments can have default value.

## Erroneous example

```{literalinclude} /sources/error_codes/3010_error/top.mbt
:language: moonbit
```

## Suggestion

Use an optional argument with `?` if you want to provide a default value:

```{literalinclude} /sources/error_codes/3010_fixed/top.mbt
:language: moonbit
```

Or remove the default value if you want to keep it as a positional argument:

```{literalinclude} /sources/error_codes/3010_fixed/top_1.mbt
:language: moonbit
```