René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Incorrect overload is used for composed function inside `pipe`","articleBody":"\u003c!-- 🚨 STOP 🚨 𝗦𝗧𝗢𝗣 🚨 𝑺𝑻𝑶𝑷 🚨\r\n\r\nHalf of all issues filed here are duplicates, answered in the FAQ, or not appropriate for the bug tracker. Even if you think you've found a *bug*, please read the FAQ first, especially the Common \"Bugs\" That Aren't Bugs section!\r\n\r\nPlease help us by doing the following steps before logging an issue:\r\n  * Search: https://github.com/Microsoft/TypeScript/search?type=Issues\r\n  * Read the FAQ: https://github.com/Microsoft/TypeScript/wiki/FAQ\r\n\r\nPlease fill in the *entire* template below.\r\n--\u003e\r\n\r\n\u003c!-- Please try to reproduce the issue with `typescript@next`. It may have already been fixed. --\u003e\r\n**TypeScript Version:**  2.9.2\r\n\r\n\u003c!-- Search terms you tried before logging this (so others can find this issue more easily) --\u003e\r\n**Search Terms:** generic function pipe contextual type wrong overload\r\n\r\n**Code**\r\n\r\nThese examples are stripped down versions of Node's `parse` function in the `querystring` module and Lodash's `values` and `fromPairs` functions.\r\n\r\nThese are issues we ran into when trying to use these functions with a `pipe` function.\r\n\r\n```ts\r\ndeclare function pipe\u003cA, B, C\u003e(ab: (a: A) =\u003e B, bc: (b: B) =\u003e C): (a: A) =\u003e C;\r\n\r\n{\r\n    type ParsedUrlQuery = { [index: string]: string };\r\n    declare function parsedUrlQueryString(str: string): ParsedUrlQuery;\r\n    declare function parsedUrlQueryString\u003cT extends {}\u003e(str: string): T;\r\n\r\n    declare const stringToString: (s: string) =\u003e string;\r\n\r\n    // $ExpectType (a: string) =\u003e ParsedUrlQuery\r\n    // but got (a: string) =\u003e {}\r\n    // Note: if we comment out the last overload for `parsedUrlQueryString`, we get the expected\r\n    // type.\r\n    const fn = pipe(\r\n        stringToString,\r\n        parsedUrlQueryString,\r\n    );\r\n}\r\n\r\n{\r\n    declare function values\u003cT\u003e(object: { [index: string]: T } | null | undefined): T[];\r\n    declare function values\u003cT extends object\u003e(object: T | null | undefined): Array\u003cT[keyof T]\u003e;\r\n    declare function values(object: any): any[];\r\n\r\n    declare const stringDictToStringDict: (\r\n        sd: { [index: string]: string },\r\n    ) =\u003e { [index: string]: string };\r\n\r\n    // $ExpectType (a: { [index: string]: string; }) =\u003e string[]\r\n    // but got (a: { [index: string]: string; }) =\u003e any[]\r\n    // Note: if we comment out the last two overloads for `values`, we get the expected type.\r\n    const fn = pipe(\r\n        stringDictToStringDict,\r\n        values,\r\n    );\r\n}\r\n\r\n{\r\n    declare function fromPairs\u003cT\u003e(pairs: [string, T][] | null | undefined): { [index: string]: T };\r\n    declare function fromPairs(pairs: any[][] | null | undefined): { [index: string]: any };\r\n\r\n    // $ExpectType (a: {}) =\u003e { [index: string]: number; }\r\n    // but got (a: {}) =\u003e { [index: string]: any; }\r\n    // Note: if we comment out the last overload for `fromPairs`, we get the expected type.\r\n    const fn = pipe(\r\n        ({  }: {}): [string, number][] =\u003e [['foo', 1]],\r\n        fromPairs,\r\n    );\r\n}\r\n```","author":{"url":"https://github.com/OliverJAsh","@type":"Person","name":"OliverJAsh"},"datePublished":"2018-07-13T11:07:14.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":19},"url":"https://github.com/25637/TypeScript/issues/25637"}