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fiskersindresorhus
fisker
and
sindresorhus
authoredFeb 2, 2023
prefer-negative-index: Check .toSpliced() and .with() (#2031)
Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>
·
v58.0.0v46.0.0
1 parent fcd8934 commit 7ed738a

6 files changed

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‎docs/rules/prefer-negative-index.md

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# Prefer negative index over `.length - index` for `{String,Array,TypedArray}#{slice,at}()` and `Array#splice()`
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# Prefer negative index over `.length - index` when possible
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💼 This rule is enabled in the ✅ `recommended` [config](https://github.com/sindresorhus/eslint-plugin-unicorn#preset-configs).
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<!-- end auto-generated rule header -->
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<!-- Do not manually modify this header. Run: `npm run fix:eslint-docs` -->
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Prefer negative index over calculating from `.length` for [`String#slice()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/slice), [`Array#slice()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice), [`TypedArray#slice()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/slice), [`String#at()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/at), [`Array#at()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at), [`TypedArray#at()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/at), and [`Array#splice()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice)
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Prefer negative index over calculating from `.length` for:
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- [`String#slice()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/slice)
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- [`Array#slice()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice)
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- [`TypedArray#slice()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/slice)
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- [`String#at()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/at)
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- [`Array#at()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at)
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- [`TypedArray#at()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/at)
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- [`Array#splice()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice)
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- [`Array#toSpliced()`](https://github.com/tc39/proposal-change-array-by-copy#overview)
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- [`Array#with()`](https://github.com/tc39/proposal-change-array-by-copy#overview)
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- [`TypedArray#with()`](https://github.com/tc39/proposal-change-array-by-copy#overview)
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<!--
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TODO: Use MDN links when available
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- [`Array#toSpliced()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/toSpliced)
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- [`Array#with()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/with)
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- [`TypedArray#with()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/with)
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-->
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## Fail
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‎readme.md

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@@ -134,7 +134,7 @@ If you don't use the preset, ensure you use the same `env` and `parserOptions` c
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| [prefer-modern-math-apis](docs/rules/prefer-modern-math-apis.md) | Prefer modern `Math` APIs over legacy patterns. | ✅ | 🔧 | |
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| [prefer-module](docs/rules/prefer-module.md) | Prefer JavaScript modules (ESM) over CommonJS. | ✅ | 🔧 | 💡 |
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| [prefer-native-coercion-functions](docs/rules/prefer-native-coercion-functions.md) | Prefer using `String`, `Number`, `BigInt`, `Boolean`, and `Symbol` directly. | ✅ | 🔧 | |
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| [prefer-negative-index](docs/rules/prefer-negative-index.md) | Prefer negative index over `.length - index` for `{String,Array,TypedArray}#{slice,at}()` and `Array#splice()`. | ✅ | 🔧 | |
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| [prefer-negative-index](docs/rules/prefer-negative-index.md) | Prefer negative index over `.length - index` when possible. | ✅ | 🔧 | |
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| [prefer-node-protocol](docs/rules/prefer-node-protocol.md) | Prefer using the `node:` protocol when importing Node.js builtin modules. | ✅ | 🔧 | |
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| [prefer-number-properties](docs/rules/prefer-number-properties.md) | Prefer `Number` static properties over global ones. | ✅ | 🔧 | 💡 |
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| [prefer-object-from-entries](docs/rules/prefer-object-from-entries.md) | Prefer using `Object.fromEntries(…)` to transform a list of key-value pairs into an object. | ✅ | 🔧 | |

‎rules/prefer-negative-index.js

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]),
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},
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],
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[
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'toSpliced',
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{
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argumentsIndexes: [0],
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supportObjects: new Set([
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'Array',
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]),
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},
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],
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[
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'at',
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{
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]),
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},
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],
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[
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'with',
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{
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argumentsIndexes: [0],
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supportObjects: new Set([
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'Array',
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...typedArray,
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]),
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},
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],
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]);
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const getMemberName = node => {
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const parentCallee = callee.object.object;
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if (
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// [].{slice,splice}
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// `[].{slice,splice,toSpliced,at,with}`
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(
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parentCallee.type === 'ArrayExpression'
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&& parentCallee.elements.length === 0
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)
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// ''.slice
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// `''.slice`
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|| (
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method === 'slice'
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&& isLiteral(parentCallee, '')
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meta: {
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type: 'suggestion',
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docs: {
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description: 'Prefer negative index over `.length - index` for `{String,Array,TypedArray}#{slice,at}()` and `Array#splice()`.',
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description: 'Prefer negative index over `.length - index` when possible.',
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},
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fixable: 'code',
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messages,

‎test/prefer-negative-index.mjs

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});
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test.snapshot({
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valid: [],
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valid: [
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// There is no `String#{toSpliced,with}`
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'String.prototype.toSpliced.call(foo, foo.length - 1)',
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'String.prototype.with.call(foo, foo.length - 1)',
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// There is no `TypedArray#toSpliced`
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'Uint8Array.prototype.toSpliced.call(foo, foo.length - 1)',
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],
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invalid: [
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'foo.slice(foo.length - 2, foo.length - 1)',
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'foo.splice(foo.length - 1, 1)',
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Array.prototype.at.call(foo, foo.length - 2);
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Array.prototype.at.apply(foo, [foo.length - 3]);
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`,
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'foo.toSpliced(foo.length - 3, foo.length - 6)',
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'Array.prototype.toSpliced.call(foo, foo.length - 3, foo.length - 6)',
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'[].toSpliced.call(foo, foo.length - 3, foo.length - 6)',
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'foo.with(foo.length - 3, foo.length - 6)',
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'Array.prototype.with.call(foo, foo.length - 3, foo.length - 6)',
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],
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});

‎test/snapshots/prefer-negative-index.mjs.md

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> 3 | Array.prototype.at.apply(foo, [foo.length - 3]);␊
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer negative index over length minus index for \`at\`.␊
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`
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## Invalid #8
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1 | foo.toSpliced(foo.length - 3, foo.length - 6)
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> Output
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`␊
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1 | foo.toSpliced(- 3, foo.length - 6)␊
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`
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> Error 1/1
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`␊
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> 1 | foo.toSpliced(foo.length - 3, foo.length - 6)␊
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer negative index over length minus index for \`toSpliced\`.␊
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`
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## Invalid #9
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1 | Array.prototype.toSpliced.call(foo, foo.length - 3, foo.length - 6)
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> Output
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`␊
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1 | Array.prototype.toSpliced.call(foo, - 3, foo.length - 6)␊
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`
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> Error 1/1
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`␊
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> 1 | Array.prototype.toSpliced.call(foo, foo.length - 3, foo.length - 6)␊
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer negative index over length minus index for \`toSpliced\`.␊
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`
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## Invalid #10
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1 | [].toSpliced.call(foo, foo.length - 3, foo.length - 6)
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> Output
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`␊
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1 | [].toSpliced.call(foo, - 3, foo.length - 6)␊
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`
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> Error 1/1
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`␊
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> 1 | [].toSpliced.call(foo, foo.length - 3, foo.length - 6)␊
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer negative index over length minus index for \`toSpliced\`.␊
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`
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## Invalid #11
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1 | foo.with(foo.length - 3, foo.length - 6)
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> Output
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`␊
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1 | foo.with(- 3, foo.length - 6)␊
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`
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> Error 1/1
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`␊
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> 1 | foo.with(foo.length - 3, foo.length - 6)␊
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer negative index over length minus index for \`with\`.␊
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`
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## Invalid #12
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1 | Array.prototype.with.call(foo, foo.length - 3, foo.length - 6)
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> Output
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`␊
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1 | Array.prototype.with.call(foo, - 3, foo.length - 6)␊
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`
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> Error 1/1
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`␊
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> 1 | Array.prototype.with.call(foo, foo.length - 3, foo.length - 6)␊
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer negative index over length minus index for \`with\`.␊
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`

‎test/snapshots/prefer-negative-index.mjs.snap

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