# E4055

Compiler diagnostic name: `field_duplicate`.

Field is already declared. Within one struct declaration, each field name must
be unique because field access, construction, and update syntax all identify a
field by name.

## Erroneous example

```{literalinclude} /sources/error_codes/4055_error/top.mbt
:language: moonbit
```

## Suggestion

Rename the field to a different name.

```{literalinclude} /sources/error_codes/4055_fixed/top.mbt
:language: moonbit
```