# E4115

Cannot auto-fill parameter of this type.

MoonBit supports and auto-filling `SourceLoc` and `ArgsLoc` parameters in
functions. Leaving the default value of parameter of other types will result in
this error.

## Erroneous example

```{literalinclude} /sources/error_codes/E4115_error/top.mbt
:language: moonbit
```

## Suggestion

Use a default value for the parameter:

```{literalinclude} /sources/error_codes/E4115_fixed/top.mbt
:language: moonbit
```