fix(prefer-optional-chain): false positive on tricky condition

[camc314]

fixes #829

[camc314]

• fix(prefer-optional-chain): false positive on tricky condition #831 👈 (View in Graphite)
• main

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[camc314]

Merge activity

• Mar 24, 5:39 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Mar 24, 5:39 PM UTC: camc314 added this pull request to the Graphite merge queue.
• Mar 24, 5:47 PM UTC: Merged by the Graphite merge queue.

[Copilot]

Pull request overview

This PR fixes a false positive in the prefer-optional-chain rule for && chains ending in a comparison where rewriting to optional chaining would change boolean semantics (notably making undefined === undefined possible and returning true where the original expression returned false). It aligns tsgolint behavior with the expected typescript-eslint behavior for the reported pattern in issue #829.

Changes:

• Add a regression test covering the “tricky condition” where the suggested optional-chain rewrite would change results when both sides can be nullish.
• Improve trailing-comparison safety detection by identifying the actual comparison “value” side using comparedExpr structural matching (instead of a simple “is access expression” heuristic).
• Replace literal/identifier heuristics for trailing comparison safety with type-based checks using new TypeInfo helpers (nullish/undefined-like and always-nullish/undefined-like).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
internal/rules/prefer_optional_chain/prefer_optional_chain.go	Refines unsafe trailing-comparison detection to avoid behavior-changing optional-chain suggestions.
internal/rules/prefer_optional_chain/prefer_optional_chain_test.go	Adds a regression test ensuring the reported false positive is not flagged.

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