Add regression test for zero-size array ICE (#10069)

[rkoivunen-sw]

Adds regression test for #10069

The test uses filecheck to verify error 99999 is emitted. Once the bug is fixed (either by rejecting zero-size arrays with a diagnostic or by handling them correctly), the test should be updated.

slangc tests/bugs/zero-size-array-nested-struct.slang -target spirv -entry computeMain -stage compute -o /dev/null
# Currently: error 99999

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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📝 Walkthrough

Walkthrough

A regression test file is added to reproduce an internal compiler error (ICE 99999) when a zero-size array is nested within a struct definition in a compute shader, targeting SPIR-V compilation.

Changes

Cohort / File(s)	Summary
Regression Test tests/bugs/zero-size-array-nested-struct.slang	New test case that defines nested structs with a zero-sized array member and a compute shader to verify ICE 99999 is emitted during SPIR-V compilation.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A test hops in to catch the error,
Zero-sized arrays, no bigger nor better,
Nested structs now traced with care,
ICE 99999? We'll find you there! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main change: adding a regression test for zero-size array ICE, directly matching the changeset content.
Description check	✅ Passed	The description directly relates to the changeset, explaining the regression test purpose and expected behavior for handling zero-size arrays.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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