# E4004

Trait methods cannot have type parameters (be polymorphic).
MoonBit currently does not support generic/polymorphic methods within trait definitions.

## Erroneous Example

```{literalinclude} /sources/error_codes/4004_error/top.mbt
:language: moonbit
```

## Suggestion

Consider using dynamic dispatch instead of generics:

```{literalinclude} /sources/error_codes/4004_fixed/top.mbt
:language: moonbit
```