# E4011

Type parameters are not allowed on default implementation for traits.

## Erroneous Example

```{literalinclude} /sources/error_codes/4011_error/top.mbt
:language: moonbit
```

The example above uses a type parameter `T` on the default implementation
of the `Stringer` trait, which is not allowed.

## Suggestion

Remove the type parameter from the default implementation:

```{literalinclude} /sources/error_codes/4011_fixed/top.mbt
:language: moonbit
```