René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"list.__add__ isn't permissive enough","articleBody":"Works at runtime, doesn't type check:\r\n\r\n```python3\r\nclass Foo:\r\n    def asd(self) -\u003e int:\r\n        return 1\r\n\r\nclass Bar:\r\n    def asd(self) -\u003e int:\r\n        return 2\r\n\r\ncombined = [Foo()] + [Bar()]\r\nfor item in combined:\r\n    print(item.asd())\r\n```\r\n\r\nI would expect `[Foo()] + [Bar()]` to produce `list[Foo | Bar]`.\r\n\r\nConverting to tuples works as expected:\r\n\r\n```python3\r\ncombined = tuple([Foo()]) + tuple([Bar()])\r\n```\r\n\r\nBut invariance problems don't apply here, because we're constructing a new list that doesn't refer to the old lists in any way.\r\n\r\nThere has previously been discussion about how mypy doesn't understand `[Foo(), Bar()]`, but this is slightly different: I'm adding lists, not mixing types within different elements of a single list literal. ","author":{"url":"https://github.com/Akuli","@type":"Person","name":"Akuli"},"datePublished":"2022-07-13T20:36:55.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/8292/typeshed/issues/8292"}