Preserve missing accessor halves when subtracting - #3121

The existing accessor test exposed the intended changed output but still asserted that the whole accessor disappeared. I updated it in 8e1d830 and expanded the case to cover reader-only, writer-only, and complete subtraction. The focused subtractor suite passes (23 tests), targeted RuboCop is clean, and git diff --check passes. The remaining ruby-head stdlib failures are shared upstream drift.

I am against subtracting only a part of attr_accessor, as it may lead to unintended behavior.

Please let me know the problem you are trying to solve.

Thanks for clarifying the intended semantics. This came from a synthetic subtraction case, not an observed application failure: an attr_accessor on one side and only one matching reader/writer declaration on the other. I assumed subtraction should retain the unmatched half, but that is a behavioral policy choice rather than a demonstrated bug. I do not have a real-world case that justifies changing that policy, so I will not push further changes based on that assumption.

The problem to be solved is unclear. Closing this.