René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Inference bug","articleBody":"``` typescript\nexport function keyOf\u003ca\u003e(value: { key: a; }): a {\n    return value.key;\n}\nexport interface Data {\n    key: number;\n    value: Date;\n}\n\nvar data: Data[] = [];\n\nexport function toKeys\u003ca\u003e(values: a[], toKey: (value: a) =\u003e string): string[] {\n    return undefined;\n}\n\ntoKeys(data, keyOf); // \u003c-- actual ok, expected error, since `keyOf` should be inferred as `number` rather than `string`\n```\n\n![image](https://cloud.githubusercontent.com/assets/937933/7476191/fbf81788-f319-11e4-9a34-82812c01f6e0.png)\n\nReproduced at playground: http://www.typescriptlang.org/Playground#src=export%20function%20keyOf%3Ca%3E(value%3A%20%7B%20key%3A%20a%3B%20%7D)%3A%20a%20%7B%0A%09return%20value.key%3B%0A%7D%0Aexport%20interface%20Data%20%7B%0A%09key%3A%20number%3B%0A%09value%3A%20Date%3B%0A%7D%0A%0Avar%20data%3A%20Data%5B%5D%20%3D%20%5B%5D%3B%0A%0Aexport%20function%20toKeys%3Ca%3E(values%3A%20a%5B%5D%2C%20toKey%3A%20(value%3A%20a)%20%3D%3E%20string)%3A%20string%5B%5D%20%7B%0A%09return%20undefined%3B%0A%7D%0A%0AtoKeys(data%2C%20keyOf)%3B%20%2F%2F%20%3C--%20expected%20compile%20error%2C%20since%20keyOf%20should%20have%20inferred%20a%20as%20%60number%60%20rather%20than%20%60string%60%0A\n","author":{"url":"https://github.com/zpdDG4gta8XKpMCd","@type":"Person","name":"zpdDG4gta8XKpMCd"},"datePublished":"2015-05-05T15:29:27.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":14},"url":"https://github.com/3038/TypeScript/issues/3038"}