Skip conversion operators for non-public types in AotConverterGenerator

[thomhurst]

Fixes #2993

[claude]

Claude finished @thomhurst's task —— View job

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Code Review Complete ✅

Reviewing PR #3148 that fixes issue #2993 for AotConverterGenerator non-public types handling.

Todo List:

• Read and understand the repository guidelines (CLAUDE.md)
• Examine the AotConverterGenerator.cs changes
• Review the new test files for coverage and quality
• Check for code quality, bugs, performance, and security issues
• Verify adherence to TUnit coding standards
• Provide comprehensive review feedback

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Review Summary

This PR properly addresses issue #2993 by preventing the AOT converter generator from attempting to generate code for non-public types, which would cause compilation failures.

Code Quality Assessment

✅ Strengths

1. Correct Fix Implementation - The changes in AotConverterGenerator.cs:78-90 properly filter out non-public types:

   • Checks containingType.DeclaredAccessibility != Accessibility.Public (line 78)
   • Also validates target type accessibility for named types (lines 85-90)
   • Excludes built-in types from the accessibility check via SpecialType.None (line 86)

2. Comprehensive Test Coverage - Both test files provide excellent coverage:

   • CompilationFailureTests.cs tests the core scenario with internal types
   • ImplicitConversionTests.cs covers various edge cases (nullable/non-nullable, nested types)
   • Tests verify both compilation success and runtime behavior

3. Follows TUnit Standards:

   • Uses modern C# features (records, file-scoped namespaces)
   • Proper test structure with async/await pattern
   • Clear, descriptive test names

✅ Security & Performance

• No security concerns - The fix prevents code generation issues without introducing vulnerabilities
• Performance impact minimal - Only adds accessibility checks during source generation (compile-time)
• No allocations in hot paths - Changes are in source generator, not runtime code

✅ Correctness

The logic correctly handles the root cause:

• AOT converters need to reference types in generated code
• Non-public types cannot be referenced from generated code in different assemblies
• The fix prevents attempting to generate such invalid code

Minor Observations

1. Comment Clarity - The comment at lines 76-77 could be more specific:

   // Current: "Skip conversion operators where the containing type is not publicly accessible"
   // Suggested: "Skip conversion operators where the containing type is not publicly accessible - generated AOT converters cannot reference non-public types"

2. Consistent Pattern - The target type check (lines 83-90) follows the same pattern as the containing type check, which is good for maintainability.

Test Quality

• Covers both the original issue scenario and additional edge cases
• Tests are focused and have clear intent
• Good use of descriptive test method names
• Proper async/await usage following TUnit patterns

Recommendation: APPROVE ✅

This PR correctly fixes the compilation issue while maintaining code quality and providing comprehensive test coverage. The solution is targeted, safe, and follows TUnit development guidelines.