gccrs: avoid ICE on generic const expressions in path resolution

[Pasta-coder]

Fixes #4302

ResolvePathRef::resolve_with_node_id assumed CONST types were always concrete values and asserted otherwise. Generic const expressions such as { N + 1 } are symbolic and cannot be evaluated prior to monomorphization, leading to an internal compiler error.

Reject non-value const kinds gracefully and emit a diagnostic instead of aborting.

gcc/testsuite:
* rust/compile/const-generic-ice-4302.rs: New test.

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[CohenArthur]

The change looks great, only a few issues but nothing bad. Once this is fixed I'm happy to merge your PR. Thanks for your contribution!

[CohenArthur]

You don't need to update the Changelog file manually - it gets updated automatically by a script every day in the upstream GCC repo :) please restore the file here or it may cause issues

[Pasta-coder]

All checks are now passing and the PR is ready for merge.

@CohenArthur Thanks a lot for the review and helpful feedback — it clarified the expected coding style and workflow. I’ll keep future PRs focused with a clean commit history.

Please let me know if there’s anything else I should adjust.

[Pasta-coder]

@P-E-P please review .

thankyou

[philberty]

Hmmm... i am not 100% sure this is the correct place to handle this because at this case is where it should be lazy evaluated and monomophized so i think this will cause false positives for other cases.

This should be handled in the typecheck pass when we resolve generic arguments instead where case cannot do N + 1 because N is not defined at this case.

[Pasta-coder]

okay , i will look into that .

thanks for pointing this out .