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chore: fix typescript skill table (#24217)

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Kayla はな
2026-04-10 17:09:07 -04:00
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parent 2f52de7cfc
commit c67c93982b
1 changed files with 29 additions and 29 deletions
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.agents/skills/deep-review/references/typescript.md
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@@ -18,35 +18,35 @@ The 5.x era resolves years of module system ambiguity and cleans house on legacy
The left column reflects patterns still common before TypeScript 5.x. Write the right column instead. The "Since" column tells you the minimum TypeScript version required.
| Old pattern | Modern replacement | Since |
| ---------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- | -------------------------------- | ------ |
| `--experimentalDecorators` + legacy decorator signatures | Standard decorators (TC39): `function dec(target, context: ClassMethodDecoratorContext)` — no flag needed | 5.0 |
| Requiring callers to add `as const` at call sites | `<const T extends HasNames>(arg: T)` — `const` modifier on type parameter | 5.0 |
| `--importsNotUsedAsValues` + `--preserveValueImports` | `--verbatimModuleSyntax` | 5.0 |
| `import { Foo } from "..."` when `Foo` is only used as a type | `import { type Foo } from "..."` or `import type { Foo } from "..."` | 5.0 |
| `"extends": "@tsconfig/strictest/tsconfig.json"` chain | `"extends": ["@tsconfig/strictest/tsconfig.json", "./tsconfig.base.json"]` (array form) | 5.0 |
| `try { ... } finally { resource.close(); resource.delete(); }` | `using resource = acquireResource()` — calls `[Symbol.dispose]()` automatically | 5.2 |
| `try { ... } finally { await resource.close() }` | `await using resource = acquireAsyncResource()` | 5.2 |
| Ad-hoc cleanup with multiple `try/finally` blocks | `using cleanup = new DisposableStack(); cleanup.defer(() => ...)` | 5.2 |
| `import data from "./data.json" assert { type: "json" }` | `import data from "./data.json" with { type: "json" }` | 5.3 |
| `.filter(Boolean)` or `.filter(x => !!x)` to remove nulls | `.filter(x => x !== undefined)` or `.filter(x => x !== null)` (infers type predicate) | 5.5 |
| Extra phantom type param to block inference bleed: `<C extends string, D extends C>` | `NoInfer<C>` on the parameter you don't want to drive inference | 5.4 |
| `/** @typedef {import("./types").Foo} Foo */` in JS files | `/** @import { Foo } from "./types" */` (JSDoc `@import` tag) | 5.5 |
| `myArray.reverse()` mutating in place | `myArray.toReversed()` (returns new array) | 5.2 |
| `myArray.sort(cmp)` mutating in place | `myArray.toSorted(cmp)` (returns new array) | 5.2 |
| `const copy = [...arr]; copy[i] = v` | `arr.with(i, v)` (returns new array) | 5.2 |
| Manual `has`/`get`/`set` pattern on `Map` | `map.getOrInsert(key, defaultValue)` or `getOrInsertComputed(key, fn)` | 6.0 RC |
| `new RegExp(str.replace(/[.\*+?^${}() | [\]\\]/g, '\\$&'))` | `new RegExp(RegExp.escape(str))` | 6.0 RC |
| `--moduleResolution node` (node10) | `--moduleResolution nodenext` (Node.js) or `--moduleResolution bundler` (bundlers/Bun) | 6.0 RC |
| `"baseUrl": "./src"` + `"@app/*": ["app/*"]` in paths | Remove `baseUrl`; use `"@app/*": ["./src/app/*"]` in paths directly | 6.0 RC |
| `module Foo { export const x = 1; }` | `namespace Foo { export const x = 1; }` | 6.0 RC |
| `export * from "..."` when all re-exported members are types | `export type * from "..."` (or `export type * as ns from "..."`) | 5.0 |
| `function f(): undefined { return undefined; }` — explicit return required in `: undefined`-returning function | Remove the `return` entirely; `undefined`-returning functions no longer require any return statement | 5.1 |
| Manual type predicate annotation on a simple arrow: `(x: T \| undefined): x is T => x !== undefined` | Remove the annotation; TypeScript infers `x is T` from `!== null/undefined` and `instanceof` checks automatically | 5.5 |
| `const val = obj[key]; if (typeof val === "string") { use(val); }` — extract to const to narrow indexed access | `if (typeof obj[key] === "string") { obj[key].toUpperCase(); }` directly — both `obj` and `key` must be effectively constant | 5.5 |
| Copy narrowed `let`/param to a `const`, or restructure code to escape stale closure narrowing after reassignment | Remove the copy; narrowing survives into closures created after the last assignment to the variable | 5.4 |
| `(arr as string[]).filter(...)` or restructure to avoid "not callable" errors on `string[] \| number[]` | Call `.filter`, `.find`, `.some`, `.every`, `.reduce` directly on union-of-array types | 5.2 |
| `if`/`else` chain used to work around lack of narrowing inside a `switch (true)` body | `switch (true)` — each `case` condition now narrows the tested variable in its clause | 5.3 |
| Old pattern | Modern replacement | Since |
| ---------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- | ------ |
| `--experimentalDecorators` + legacy decorator signatures | Standard decorators (TC39): `function dec(target, context: ClassMethodDecoratorContext)` — no flag needed | 5.0 |
| Requiring callers to add `as const` at call sites | `<const T extends HasNames>(arg: T)` — `const` modifier on type parameter | 5.0 |
| `--importsNotUsedAsValues` + `--preserveValueImports` | `--verbatimModuleSyntax` | 5.0 |
| `import { Foo } from "..."` when `Foo` is only used as a type | `import { type Foo } from "..."` or `import type { Foo } from "..."` | 5.0 |
| `"extends": "@tsconfig/strictest/tsconfig.json"` chain | `"extends": ["@tsconfig/strictest/tsconfig.json", "./tsconfig.base.json"]` (array form) | 5.0 |
| `try { ... } finally { resource.close(); resource.delete(); }` | `using resource = acquireResource()` — calls `[Symbol.dispose]()` automatically | 5.2 |
| `try { ... } finally { await resource.close() }` | `await using resource = acquireAsyncResource()` | 5.2 |
| Ad-hoc cleanup with multiple `try/finally` blocks | `using cleanup = new DisposableStack(); cleanup.defer(() => ...)` | 5.2 |
| `import data from "./data.json" assert { type: "json" }` | `import data from "./data.json" with { type: "json" }` | 5.3 |
| `.filter(Boolean)` or `.filter(x => !!x)` to remove nulls | `.filter(x => x !== undefined)` or `.filter(x => x !== null)` (infers type predicate) | 5.5 |
| Extra phantom type param to block inference bleed: `<C extends string, D extends C>` | `NoInfer<C>` on the parameter you don't want to drive inference | 5.4 |
| `/** @typedef {import("./types").Foo} Foo */` in JS files | `/** @import { Foo } from "./types" */` (JSDoc `@import` tag) | 5.5 |
| `myArray.reverse()` mutating in place | `myArray.toReversed()` (returns new array) | 5.2 |
| `myArray.sort(cmp)` mutating in place | `myArray.toSorted(cmp)` (returns new array) | 5.2 |
| `const copy = [...arr]; copy[i] = v` | `arr.with(i, v)` (returns new array) | 5.2 |
| Manual `has`/`get`/`set` pattern on `Map` | `map.getOrInsert(key, defaultValue)` or `getOrInsertComputed(key, fn)` | 6.0 RC |
| `new RegExp(str.replace(/[.\*+?^${}()\[\]\\]/g, '\\$&'))` | `new RegExp(RegExp.escape(str))` | 6.0 RC |
| `--moduleResolution node` (node10) | `--moduleResolution nodenext` (Node.js) or `--moduleResolution bundler` (bundlers/Bun) | 6.0 RC |
| `"baseUrl": "./src"` + `"@app/*": ["app/*"]` in paths | Remove `baseUrl`; use `"@app/*": ["./src/app/*"]` in paths directly | 6.0 RC |
| `module Foo { export const x = 1; }` | `namespace Foo { export const x = 1; }` | 6.0 RC |
| `export * from "..."` when all re-exported members are types | `export type * from "..."` (or `export type * as ns from "..."`) | 5.0 |
| `function f(): undefined { return undefined; }` — explicit return required in `: undefined`-returning function | Remove the `return` entirely; `undefined`-returning functions no longer require any return statement | 5.1 |
| Manual type predicate annotation on a simple arrow: `(x: T \| undefined): x is T => x !== undefined` | Remove the annotation; TypeScript infers `x is T` from `!== null/undefined` and `instanceof` checks automatically | 5.5 |
| `const val = obj[key]; if (typeof val === "string") { use(val); }` — extract to const to narrow indexed access | `if (typeof obj[key] === "string") { obj[key].toUpperCase(); }` directly — both `obj` and `key` must be effectively constant | 5.5 |
| Copy narrowed `let`/param to a `const`, or restructure code to escape stale closure narrowing after reassignment | Remove the copy; narrowing survives into closures created after the last assignment to the variable | 5.4 |
| `(arr as string[]).filter(...)` or restructure to avoid "not callable" errors on `string[] \| number[]` | Call `.filter`, `.find`, `.some`, `.every`, `.reduce` directly on union-of-array types | 5.2 |
| `if`/`else` chain used to work around lack of narrowing inside a `switch (true)` body | `switch (true)` — each `case` condition now narrows the tested variable in its clause | 5.3 |
## New capabilities