# `layout.file_name_mismatch`

File name does not match its declaration.

Area 1, [Project layout and modules](../topics/project-layout-and-modules.md); not declinable; the next step is usually the agent's.

```jadpo
type DueDate = CalendarDate {}
```

```text
error: `DueDate` is in `due.jadpo`
 --> domains/planning/types/due.jadpo:1:6
  |
1 | type DueDate = CalendarDate {}
  |      ^^^^^^^ file name should be `due_date.jadpo`
  reason: A file is named after the declaration it holds, so a search for a name finds its file.
  next: Rename `due.jadpo` to `due_date.jadpo` (agent)
  rule: layout.file_name_mismatch
  help: https://jadpo.dev/docs/errors/layout.file_name_mismatch

check failed: 1 error, 3 files
```