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@Use("java")

Klar uses @Use to declare the backend target for a function.

Today:

  • @Use is mandatory on all functions.
  • Only @Use("java") is supported.

This is by design: explicitness over convention.

Example​

@Use("java")
public void main(){
    println("Hello!");

    return null;
}

Missing annotation​

If you omit @Use, Klar emits a syntax diagnostic like:

[K:E113] MissingAnnotation
ERROR (SYNTAX)
...
Expected:
  '@Use'

Unsupported target​

If you specify an unsupported backend target:

@Use("python")
public void main(){
    return null;
}

Klar emits a backend diagnostic:

[K:E400] UnknownBackendTarget
ERROR (BACKEND)
...
Cause:
  Unsupported backend target 'python'
Fix:
  Use a supported backend (currently only 'java' is supported)

Roadmap​

Planned: interoperability starting with JSON interop.

Additional backends exist as a long-term direction, not a current promise.