@sap/cds-compiler/share/messages/anno-missing-rewrite.md

CDS (Core Data Services) compiler and backends

# anno-missing-rewrite

A propagated annotation containing expressions can't be rewritten and would
end up with invalid paths.

While propagating annotations containing expressions such as `@anno: (path)`,
the compiler ensures that the path remains valid.  If necessary, the paths
have to be rewritten, e.g. when being propagated to projections that rename
their source's elements.  If rewriting is not possible, this error is emitted.

## Example

Erroneous code example:

```cds
type T : {
    @anno: (sibling)
    elem: String;
    sibling: String;
};
type TString : T:elem; // ❌ there is no `sibling`
```

The annotating `@anno` would be propagated to `TString`.  However, because its
path refers to an element that is not reachable at `TString`, the path can't
be rewritten and compilation fails.

## How to Fix

Explicitly override the annotation.  Either remove it by setting its value to
`null` or by using another value.

```cds
// (1) direct annotation
@anno: null
type TString : T:elem;

// (2) annotate statement
type TString : T:elem;
annotate TString with @(anno: null);
```

Variant (1) may not always be applicable, e.g. if annotations in a structured
type would need to be overridden.  In those cases, use variant (2) and assign
annotations via the `annotate` statement.