fix(eslint-plugin): [no-redundant-type-constituents] incorrectly marks & string as redundant

[arka1002]

fixes: #7580

PR Checklist

• Addresses an existing open issue: fixes Bug: no-redundant-type-constituents incorrectly marks & string as redundant #7580
• That issue was marked as accepting prs
• Steps in Contributing were taken

Overview

[typescript-eslint]

Thanks for the PR, @arka1002!

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[JoshuaKGoldberg]

Ok! This rule is trickier than I remembered it being 😅 nice job adding to its logic. Thanks for sending this!

I think I understand what the new code is doing, but it was a little hard to read through. A couple general suggestions:

• Try to stick with the existing conventions in code unless there's a strong reason to deviate
• Try to use informative names when possible, not general ones like key or iterator

The core logic seems reasonable to me. Requesting changes on refactors. There might be a point where more tests would be reasonable depending on one or two of them?

[JoshuaKGoldberg]

[Style] Is there a need to have a shared variable outside the forEach? Switching it to being inside the .forEach and never modified doesn't fail any unit tests:

Suggested change

	value.forEach(union => {
	typeFlagsOfUnions.push(union.typeFlags);
	});
	const typeFlagsOfUnions = unionTypeFlags.flatMap(
	union =>
	union.typeFlags as keyof typeof literalToPrimitiveTypeFlags,
	);

That includes an extra tip: since we know the type flags are all the keyof typeof literalToPrimitiveTypeFlags, using the assertion early on means we don't need multiple assertions later.

[arka1002]

I removed the variable, I dont think we need it anymore.
I might need some help with the type assertions though 😅

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✅ Successfully ran 31 targets

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

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.07%. Comparing base (025e892) to head (52783f0).
Report is 43 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8282      +/-   ##
==========================================
- Coverage   87.84%   87.07%   -0.77%     
==========================================
  Files         397      251     -146     
  Lines       13844    12285    -1559     
  Branches     4073     3871     -202     
==========================================
- Hits        12161    10697    -1464     
+ Misses       1381     1316      -65     
+ Partials      302      272      -30     

Flag	Coverage Δ
unittest	87.07% <100.00%> (-0.77%)	⬇️

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

Files	Coverage Δ
...plugin/src/rules/no-redundant-type-constituents.ts	93.91% <100.00%> (+0.78%)	⬆️

... and 146 files with indirect coverage changes

[bradzacher]