# Diagnostics

AspectGenerator diagnostics are intended to report user mistakes before generated code fails to compile.

## Existing Diagnostics

- `AG0001`: `OnCall` aspect must be last when the aspect is applied directly.
- `AG0002`: `OnCall` aspect must be last when the aspect is inferred from method metadata.
- `AG0003`: invocation cannot be intercepted by the compiler.
- `AG0004`: generated interceptor namespace is not listed in `InterceptorsNamespaces`.

## Planned Hook Contract Diagnostics

- `AG0101`: hook method not found.
- `AG0102`: hook method must be static.
- `AG0103`: invalid hook parameter type.
- `AG0104`: invalid hook return type.
- `AG0105`: `OnCall` signature mismatch.
- `AG0106`: `UseInterceptData=true` requires `ref InterceptData<T>`.
- `AG0107`: async hook requires a supported async target.

## Planned InterceptMethods Diagnostics

- unmatched method display string;
- ambiguous match;
- alias-sensitive match requiring a more precise spelling.