fix(eslint-plugin): [no-unnecessary-type-assertion] handle exactOptionalPropertyTypes compiler option

[yeonjuan]

PR Checklist

• Addresses an existing open issue: fixes Bug: [no-unnecessary-type-assertion] false negative with exactOptionalPropertyTypes compiler option #5344
• That issue was marked as accepting prs
• Steps in Contributing were taken

Overview

[typescript-eslint]

Thanks for the PR, @yeonjuan!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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✅ Successfully ran 31 targets

• nx test eslint-plugin
• nx test eslint-plugin --coverage=false
• nx run types:build
• nx test utils
• nx test type-utils
• nx run repo-tools:postinstall-script
• nx test visitor-keys
• nx test typescript-eslint
• nx test rule-schema-to-typescript-types
• nx test typescript-estree --coverage=false
• nx test typescript-estree
• nx test eslint-plugin-internal --coverage=false
• nx test repo-tools
• nx test ast-spec
• nx run-many --target=build --parallel --exclude=website --exclude=website-eslint
• nx test eslint-plugin-internal
• nx test scope-manager
• nx test parser
• nx run-many --target=lint --parallel --exclude eslint-plugin
• nx run-many --target=typecheck --parallel
• nx test rule-schema-to-typescript-types --coverage=false
• nx test type-utils --coverage=false
• nx test visitor-keys --coverage=false
• nx test utils --coverage=false
• nx test scope-manager --coverage=false
• nx test typescript-eslint --coverage=false
• nx run repo-tools:generate-configs
• nx test ast-spec --coverage=false
• nx test parser --coverage=false
• nx test repo-tools --coverage=false
• nx run integration-tests:test

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.37%. Comparing base (2a62a40) to head (72a9a55).
Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8770      +/-   ##
==========================================
+ Coverage   87.34%   87.37%   +0.03%     
==========================================
  Files         254      255       +1     
  Lines       12474    12509      +35     
  Branches     3915     3926      +11     
==========================================
+ Hits        10895    10930      +35     
  Misses       1304     1304              
  Partials      275      275              

Flag	Coverage Δ
unittest	87.37% <100.00%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...-plugin/src/rules/no-unnecessary-type-assertion.ts	97.56% <100.00%> (+0.45%)	⬆️

... and 2 files with indirect coverage changes

[JoshuaKGoldberg]

LGTM, nice find! Good to see this venerable issue tackled. 🚀

The logic looks good, just a couple of small non-blocking suggestions from me. Someone else should probably take another look though - these type union shenanigans can get hard to reason about.

[auvred]

LGTM 🚀