feat(typescript-estree): split TSMappedType typeParameter into constraint and key

[JoshuaKGoldberg]

BREAKING CHANGE:
Deprecates an existing property on the AST

PR Checklist

• Addresses an existing open issue: fixes AST cleanup: type parameter in TSMappedType #6433
• That issue was marked as accepting prs
• Steps in Contributing were taken

Overview

Per the issue, deprecates the typeParameter property in favor of constraint and key properties.

[typescript-eslint]

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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.

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✅ Successfully ran 31 targets

• Node 20 - nx test eslint-plugin
• Node 16 - nx test eslint-plugin --coverage=false
• nx run-many --target=lint --parallel
• Node 20 - nx test typescript-estree
• Node 20 - nx test scope-manager
• Node 20 - nx test type-utils
• Node 20 - nx test visitor-keys
• Node 20 - nx run types:build
• Node 20 - nx test utils
• Node 20 - nx test rule-schema-to-typescript-types
• Node 20 - nx test repo-tools
• nx run integration-tests:test
• Node 16 - nx test typescript-estree --coverage=false
• nx run-many --target=typecheck --parallel
• Node 20 - nx test ast-spec
• Node 16 - nx test ast-spec --coverage=false
• Node 20 - nx test parser
• Node 16 - nx test type-utils --coverage=false
• Node 16 - nx test eslint-plugin-tslint --coverage=false
• Node 16 - nx test eslint-plugin-internal --coverage=false
• Node 16 - nx test scope-manager --coverage=false
• Node 20 - nx test eslint-plugin-internal
• Node 20 - nx test eslint-plugin-tslint
• Node 16 - nx run types:build
• nx run types:build
• Node 16 - nx test repo-tools --coverage=false
• Node 16 - nx test visitor-keys --coverage=false
• Node 16 - nx test parser --coverage=false
• Node 16 - nx test rule-schema-to-typescript-types --coverage=false
• Node 16 - nx test utils --coverage=false
• nx run-many --target=build --parallel --exclude=website --exclude=website-eslint

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[codecov]

Codecov Report

Merging #7065 (933e00a) into v6 (c8bb00d) will increase coverage by 0.02%.
The diff coverage is 83.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##               v6    #7065      +/-   ##
==========================================
+ Coverage   87.51%   87.53%   +0.02%     
==========================================
  Files         375      375              
  Lines       13148    13153       +5     
  Branches     3894     3894              
==========================================
+ Hits        11506    11514       +8     
+ Misses       1262     1256       -6     
- Partials      380      383       +3     

Flag	Coverage Δ
unittest	87.53% <83.33%> (+0.02%)	⬆️

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

Impacted Files	Coverage Δ
packages/visitor-keys/src/visitor-keys.ts	100.00% <ø> (ø)
packages/typescript-estree/src/convert.ts	30.60% <75.00%> (+0.57%)	⬆️
packages/eslint-plugin/src/rules/indent.ts	88.09% <100.00%> (ø)
...s/eslint-plugin/src/util/collectUnusedVariables.ts	93.16% <100.00%> (ø)
...ckages/scope-manager/src/referencer/TypeVisitor.ts	98.03% <100.00%> (+0.05%)	⬆️

[bradzacher]

this change introduces a bug into the scope analysis because previously it used to implicitly rely on the fact that typeParameter was a TSTypeParemeter - i.e. declared a type variable.

So now we'll need to update our visitor so that we declare the key as a type variable, then visit the constraint, then the name type, then the type annotation.

typescript-eslint/packages/scope-manager/src/referencer/TypeVisitor.ts

Lines 198 to 203 in 2f46341

	protected TSMappedType(node: TSESTree.TSMappedType): void {
	// mapped types key can only be referenced within their return value
	this.#referencer.scopeManager.nestMappedTypeScope(node);
	this.visitChildren(node);
	this.#referencer.close(node);
	}

[JoshuaKGoldberg]

We didn't make it in time. I'll move this to v7.

[JoshuaKGoldberg]

This was unintentionally auto-closed when we merged the v6 branch 🙃 it'll be recreated.

[JoshuaKGoldberg]

Or, actually, since this needs to wait till v7 anyway - I'll just leave it closed.

[JoshuaKGoldberg]

Since this rule is getting removed in #8074 anyway.

[bradzacher]

overall looks good - one definite bug to fix though.