# What is built

The compiler builds the decided layout, with each rule's real output under
[Errors](project-layout-and-modules.md#errors).

| Feature | Status |
|---|---|
| Root, domains and their folders | Built: a file where the layout has no place for it is `layout.unknown_location`, and a declaration in the wrong folder `layout.wrong_folder`; a folder or file with no `app.jadpo` above it is checked as loose files. Not built yet: `jadpo domain rename`, `split` and `merge`; the `documents` capability, so a file in `documents/` is `layout.unknown_location` until it is. |
| Files and names | Built: one primary declaration per file, named after it; names unique project-wide; the round-trip and folded-collision rules, with the exception for a type folding to its callable's name. |
| Names per domain | Partly built: private functions and types unique only within their domain, each domain's code reading its own; their identity keys carrying the domain, with promotion to `shared/` writing a registry line; `semantic.duplicate_declaration` saying copy or clash and listing the names in use with the same words. `jadpo rename` is not built yet ([Commands for looking into and changing code](commands-for-looking-into-and-changing-code.md)). |
| Order independence | Built: declaration and file order never matter. |
| Domains, `public` and calls | Built: owner-qualified calls and per-declaration `public`, with `visibility.private_cross_domain`, `visibility.public_not_allowed` and `visibility.public_unused`. |
| Reserved words | Built: a reserved word can't name anything. |
| Comments | Built: `//` and `///` documentation comments. |
| Similar helpers | Built: `library.similar_exists`, a declinable error. Not built yet: `jadpo impact`. |
| Declinable errors | Partly built: no warning severity; the `decline <rule>: "<reason>"` line with `decline.unused`, `decline.not_declinable` and `decline.no_reason`; `jadpo declines list` and `clear`; the editor's "Decline with a reason" and "Remove decline". Not built yet: `jadpo approval` ([Records and manifest](records-and-manifest.md)) and the date rule for expired [feature flags](feature-flags.md). |
| Constants | Built: `constant` as a reserved word and a declaration placed and shared as helper functions are, a private one unique within its domain, `constant.similar_exists`, and a top-level `var` pointed at `constant` ([Constants](constants.md)). |
| Imports | Built: `use <folder> { Names }` and `use <domain>`, with `import.missing`, `import.unknown`, `import.unused`, `import.unneeded` and `import.duplicate`; `jadpo fmt` adds, removes and sorts imports, `jadpo fmt --layout` makes promotion moves, and go to definition works from every use of a name, a `use` line's included. |
| A file holds only what its primary declaration uses | Built: `layout.unused_declaration` for a supporting declaration the primary declaration doesn't use, directly or through one another. |
| Definition before use | Built: `jadpo fmt` writes each file's declarations before the first one that uses them, and `jadpo fmt --check` fails on a file out of that order. |
| Referenced assets | Not built yet: `layout.asset_unreferenced` waits for the ways [Integrations](external-services.md) and [Built-in services](built-in-services.md) refer to files that aren't Jadpo. |
| Jadpo version | Built: `application { jadpo: "0.1" }`, with `toolchain.version_newer` refusing a project on a later line, `toolchain.version_older` one on an earlier line, each naming the release to install, and `toolchain.version_invalid`; the installed `jadpo` runs the release the line or `jadpo.lock`'s pin names ([Which jadpo runs](which-jadpo-runs.md)). `jadpo new` writes the line of the `jadpo` that ran it. |
| Packages | Built: the root `packages/` and `jadpo.lock`, `shared/providers/`, packages checked as `shared/` is, `use packages/<name>`, and the reachable-from-public rule (`visibility.public_reaches_private`) in domains and packages; [Integrations](external-services.md) records the choices. |