[code-reflection] RFR: Improved error message on OpenCLBackend if Reflect annotation is missing on transitive methods from kernel method

[duke]

On Wed, 31 Dec 2025 00:04:04 GMT, Nadeesh TV <ntv at openjdk.org> wrote:

> **Description** 
> Currently, if we miss the **@Reflec**t annotation on methods called from kernel functions, no method is generated for them in the corresponding backend. This causes an error like:
> 
> `> error: implicit declaration of function 'squareitWithoutReflectAnnotation' is invalid...
> `
> **Solution** 
> - Improved the error message by adding:  *"Did you miss @Reflect annotation on the above function?"* for such cases.
> 
>    - Tried throwing an early error on the Java side, but calls to certain methods (e.g., `hat.buffer.S32Array.length()`) lack @Reflect annotations yet map to native functions later. Therefore, I could not find an easy early Java-side validation.
> 
> **Test** 
>   -  A new test is added at **hat.test.TestMissingReflectAnnotation#testTransitiveMethoFromKernelWithoutReflectAnnotation**
>   - Output of the test case
> 
> UNSUPPORTED (log once): buildComputeProgram: cl2Metal failed
> buildStatus = failed
> logLen = 234 log  = program_source:68:37: error: implicit declaration of function 'squareitWithoutReflectAnnotation' is invalid in OpenCL
>         array->array[(long)HAT_GIX]=squareitWithoutReflectAnnotation(value);
>                                     ^
> 
> Did you miss @Reflect annotation on the above function?
> 
> Class: hat.test.TestMissingReflectAnnotation
> Testing: #testComputeMethodWithoutReflectAnnotation..................... [passed]
> Testing: #testKernelMethodWithoutReflectAnnotation..................... [passed]
> Testing: #testTransitiveMethoFromKernelWithoutReflectAnnotation..................... [passed]
> 
> passed: 3, failed: 0, unsupported: 0, precision-errors: 0

@deleSerna 
Your change (at version 0afd2a0ce928acee1260582a65de4e5e4d88f203) is now ready to be sponsored by a Committer.

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PR Comment: https://git.openjdk.org/babylon/pull/798#issuecomment-3700904410