René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Ghost error appearing after signature help in inferred signatures with rest parameter","articleBody":"### 🔎 Search Terms\n\nsignature help inference signature rest spread nested \n\n### 🕗 Version \u0026 Regression Information\n\n- This is the behavior in every version I tried\n\n### ⏯ Playground Link\n\nhttps://www.typescriptlang.org/play/?ts=6.0.0-dev.20250803#code/KYDwDg9gTgLgBASwHY2FAZgQwMbDgBQTGEwCMAbPAbwCg44wjgAeAQQBo4AhOAXjiTAAbmgB8AChgALBAGcAXHA5wyi8QH1FrAJR9R3bYq4BuGgF8aNGAE9icAMIQhmKAkwo2+-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-GNpgsLZu2uW5+weeByAgC9-W2AA6bCIWAS0Y2ARRSl2RpWCTTBrGYdxrFEN89CeF5+SECBJ04GUoDYsUoDg0BIFgJDB3gbBMFQTpoDtWQAGlgCafgACIAAFgEYjIAHo0B-VThNE8S8Lk0JeOgeBLgQvsB0eH0EGkewROAMSoGsRRmBsnTXDwrcK2VMioAo5h8GTYhYGsaSaNPehsMw7S7N0hQHFs+yJLooI4DYKBOmVbNK283zqNETVgBgTh7A8ndlSoUU-XECKXHSrQ0tkQNiPgMwwocYYkv0YqADJ8W9YBKuq+q6vSxqCrgHqQLgEkooSvCQrpfEppcxAkDi1yJJJJBUihNAaQW5k8DMGCzgM8AjLgGw7FYchyBCq1NhFAoSpzcrpvimL5sUZBXigOAAEU4Aseh5zgABrGSIHQf7tl8LjTEM-jLrwApyx8jJrvIDYipEjLtxzfyIECmwQq8Nbcc8lQkGsbYQZRlIcEydlXpmj6ZIW17JJWsmFuowHAdo+hYf8U6+OMntEPMoSROwKQXOihynO2Iptkltb5Yk56svIyiMbujZRDy7ZWAAJmvApTe2UpjZPcQsOwmrYpJHU4AiuXZtka96HQNQNMUOm0ZgDGsbV93Nu20hdtEd8+QyNhTaeeOrYFuAaQ6lLlHKW36GUikYD9lTWWxDk05jiY4AAHyUePzYrp4QGuVJLmD-2GaD9k3ZisOdqgGkDc1Wuk9CBDLSDCAIG-aBNeVT9Rx-ANxDk60x4nqA5M4KgzG0TDGGILO4Es6z3oche6ghTBkDk7Q6I3yxh+VLgXBXqeoNjL8xygee5IfqAV7Xo0t53sAPeB9ZZH2sAvcE7RgAQj-nJU+58kCX2vucO+3BMAAC8n6ZWnjGEcK9P4P0we-P+G8AFMGAVZUBrlwFyUgagGBV9dA33gr2O4yE4CkAwWobYIBfDhzQCXAuzB2JFmXu-Wu38n6V0ISvTi-geJnX4qrMAyZOg+QhCKTh6DxAAEYyG720jLDux84EQDPhfTgGh3yoU6BoTCEFOjaCcaESwri3FAA\n\n### 💻 Code\n\n```ts\n/// \u003creference path=\"fourslash.ts\" /\u003e\n\n// @strict: true\n// @target: esnext\n// @lib: esnext\n\n//// export interface Pipeable {\n////   pipe\u003cA, B = never\u003e(this: A, ab: (_: A) =\u003e B): B;\n//// }\n////\n//// type Covariant\u003cA\u003e = (_: never) =\u003e A;\n////\n//// interface VarianceStruct\u003cout A, out E, out R\u003e {\n////   readonly _V: string;\n////   readonly _A: Covariant\u003cA\u003e;\n////   readonly _E: Covariant\u003cE\u003e;\n////   readonly _R: Covariant\u003cR\u003e;\n//// }\n////\n//// declare const EffectTypeId: unique symbol;\n////\n//// interface Variance\u003cout A, out E, out R\u003e {\n////   readonly [EffectTypeId]: VarianceStruct\u003cA, E, R\u003e;\n//// }\n////\n//// interface Effect\u003cout A, out E = never, out R = never\u003e\n////   extends Variance\u003cA, E, R\u003e,\n////     Pipeable {}\n////\n//// interface Class\u003cFields\u003e extends Pipeable {\n////   new (): Fields;\n//// }\n////\n//// interface TaggedErrorClass\u003cTag extends string, Fields\u003e extends Class\u003cFields\u003e {\n////   readonly _tag: Tag;\n//// }\n////\n//// declare const TaggedError: (identifier?: string) =\u003e \u003c\n////   Tag extends string,\n////   Fields\n//// \u003e(\n////   tag: Tag,\n////   fieldsOr: Fields\n//// ) =\u003e TaggedErrorClass\u003c\n////   Tag,\n////   {\n////     readonly _tag: Tag;\n////   }\n//// \u003e;\n////\n//// declare const log: (\n////   ...message: ReadonlyArray\u003cany\u003e\n//// ) =\u003e Effect\u003cvoid, never, never\u003e;\n////\n//// export const categoriesKey = \"@effect/error/categories\";\n////\n//// export declare const withCategory: \u003cCategories extends Array\u003cPropertyKey\u003e\u003e(\n////   ...categories: Categories\n//// ) =\u003e \u003cArgs extends Array\u003cany\u003e, Ret, C extends { new (...args: Args): Ret }\u003e(\n////   C: C\n//// ) =\u003e C \u0026 {\n////   new (...args: Args): Ret \u0026 {\n////     [categoriesKey]: { [Cat in Categories[number]]: true };\n////   };\n//// };\n////\n//// export type AllKeys\u003cE\u003e = E extends { [categoriesKey]: infer Q }\n////   ? keyof Q\n////   : never;\n//// export type ExtractAll\u003cE, Cats extends PropertyKey\u003e = Cats extends any\n////   ? Extract\u003cE, { [categoriesKey]: { [K in Cats]: any } }\u003e\n////   : never;\n////\n//// export declare const catchCategory: \u003c\n////   E,\n////   const Categories extends Array\u003cAllKeys\u003cE\u003e\u003e,\n////   A2,\n////   E2,\n////   R2\n//// \u003e(\n////   ...args: [\n////     ...Categories,\n////     f: (err: ExtractAll\u003cE, Categories[number]\u003e) =\u003e Effect\u003cA2, E2, R2\u003e\n////   ]\n//// ) =\u003e \u003cA, R\u003e(\n////   effect: Effect\u003cA, E, R\u003e\n//// ) =\u003e Effect\u003cA | A2, E2 | Exclude\u003cE, ExtractAll\u003cE, Categories[number]\u003e\u003e, R | R2\u003e;\n////\n//// class FooError extends TaggedError()(\"FooError\", {}).pipe(\n////   withCategory(\"domain\")\n//// ) {}\n////\n//// class BarError extends TaggedError()(\"BarError\", {}).pipe(\n////   withCategory(\"system\", \"domain\")\n//// ) {}\n////\n//// class BazError extends TaggedError()(\"BazError\", {}).pipe(\n////   withCategory(\"system\")\n//// ) {}\n////\n//// declare const baz: (\n////   x: number\n//// ) =\u003e Effect\u003cnever, FooError | BarError | BazError, never\u003e;\n////\n//// export const program = baz(1).pipe(catchCategory(\"domain\",/*1*/ (_) =\u003e log(_._tag)));\n\nverify.getSemanticDiagnostics([]);\ngoTo.marker(\"1\");\nedit.insert(\",\");\nverify.signatureHelpPresentForTriggerReason({\n    kind: \"characterTyped\",\n    triggerCharacter: \",\",\n});\nedit.backspace(1);\nverify.signatureHelpPresentForTriggerReason({\n    kind: \"retrigger\",\n});\nverify.getSemanticDiagnostics([]);\n```\n\n\n### 🙁 Actual behavior\n\nIt's sometimes a little bit tricky to reproduce it in the playground but steps are pretty easy:\n1. position ur cursor after `\"domain\",` in the last statement\n2. insert `,`\n3. this should trigger the signature help\n4. now remove the inserted comma character\n5. the signature help should still be visible at this point\n6. error is reported\n\n### 🙂 Expected behavior\n\nGiven the code is exactly the same at the step 6 as it is before any steps are taken, I don't expect this code to report any errors. Any edit outside of the `catchCategory`'s argument list makes the error go away (a further indication the error should not be there) but edits inside that argument list don't make it go away.\n\n### Additional information about the issue\n\n_No response_","author":{"url":"https://github.com/Andarist","@type":"Person","name":"Andarist"},"datePublished":"2025-08-03T11:41:26.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/62183/TypeScript/issues/62183"}