fix(eslint-plugin): [no-unnecessary-type-assertion] combine template literal check with const variable check

[abrahamguo]

PR Checklist

• Addresses an existing open issue: fixes Bug: [no-unnecessary-type-assertion] (regression) false positives on template literals with no expressions #8819, Bug: [@typescript-eslint/no-unnecessary-type-assertion] False positives for "as const" assertions #8721
• That issue was marked as accepting prs
• Steps in Contributing were taken

Overview

In #8740, new logic was added for template literals. This logic was wrongly added as a precondition, when it needs to be combined with the existing const variable declaration logic.

• Fix failing case from Bug: [no-unnecessary-type-assertion] (regression) false positives on template literals with no expressions #8819 by re-arranging conditions
• The type assertions in the valid tests added in fix(eslint-plugin): [no-unnecessary-type-assertion] avoid remove const casting on template literals with expressions inside #8740 are actually unnecessary (but are too complex to be detected by the current logic). Changed const to let, so that the type assertions are truly necessary.
• Improved the name of isLiteralVariableDeclarationChangingTypeWithConst to isImplicitlyNarrowedConstDeclaration.

[typescript-eslint]

Thanks for the PR, @abrahamguo!

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!

---

🙏 Please, if you or your company is finding typescript-eslint valuable, help us sustain the project by sponsoring it transparently on https://opencollective.com/typescript-eslint.

[netlify]

✅ Deploy Preview for typescript-eslint ready!

Name	Link
🔨 Latest commit	d8f2fe7
🔍 Latest deploy log	https://app.netlify.com/sites/typescript-eslint/deploys/660b661027b6d80008511550
😎 Deploy Preview	https://deploy-preview-8820--typescript-eslint.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
Lighthouse	1 paths audited Performance: 92 (🟢 up 1 from production) Accessibility: 100 (no change from production) Best Practices: 92 (no change from production) SEO: 98 (no change from production) PWA: 80 (no change from production) View the detailed breakdown and full score reports

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[nx-cloud]

☁️ Nx Cloud Report

CI is running/has finished running commands for commit d8f2fe7. As they complete they will appear below. Click to see the status, the terminal output, and the build insights.

📂 See all runs for this CI Pipeline Execution

---

✅ Successfully ran 31 targets

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

---

Sent with 💌 from NxCloud.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.37%. Comparing base (a14ba9d) to head (d8f2fe7).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8820      +/-   ##
==========================================
- Coverage   88.02%   87.37%   -0.65%     
==========================================
  Files         405      255     -150     
  Lines       14089    12510    -1579     
  Branches     4125     3927     -198     
==========================================
- Hits        12402    10931    -1471     
+ Misses       1382     1304      -78     
+ Partials      305      275      -30     

Flag	Coverage Δ
unittest	87.37% <100.00%> (-0.65%)	⬇️

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	97.53% <100.00%> (-0.04%)	⬇️

... and 150 files with indirect coverage changes