René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[2.0 regression] Crash with --allow-redefinition on partial type with global","articleBody":"```\nλ cat test250.py\nx = []\n\ndef f() -\u003e None:\n    global x\n    x\n```\n\n```\nλ mypy --no-incremental --show-traceback --allow-redefinition test250.py\ntest250.py:5: error: INTERNAL ERROR -- Please try using mypy master on GitHub:\nhttps://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build\nPlease report a bug at https://github.com/python/mypy/issues\nversion: 2.1.0+dev.16823a17c10ce5a00b0bbdee5fa9959dccea8ccc\nTraceback (most recent call last):\n  File \"/Users/shantanu/.virtualenvs/mypy-fexc/bin/mypy\", line 10, in \u003cmodule\u003e\n    sys.exit(console_entry())\n  File \"/Users/shantanu/dev/mypy/mypy/__main__.py\", line 16, in console_entry\n    main()\n  File \"/Users/shantanu/dev/mypy/mypy/main.py\", line 154, in main\n    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)\n  File \"/Users/shantanu/dev/mypy/mypy/main.py\", line 244, in run_build\n    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)\n  File \"/Users/shantanu/dev/mypy/mypy/build.py\", line 422, in build\n    result = build_inner(\n  File \"/Users/shantanu/dev/mypy/mypy/build.py\", line 537, in build_inner\n    graph = dispatch(sources, manager, stdout, connect_threads)\n  File \"/Users/shantanu/dev/mypy/mypy/build.py\", line 4150, in dispatch\n    process_graph(graph, manager)\n  File \"/Users/shantanu/dev/mypy/mypy/build.py\", line 4618, in process_graph\n    done, still_working, results = manager.wait_for_done(graph)\n  File \"/Users/shantanu/dev/mypy/mypy/build.py\", line 1492, in wait_for_done\n    process_stale_scc(graph, next_scc, self)\n  File \"/Users/shantanu/dev/mypy/mypy/build.py\", line 4792, in process_stale_scc\n    graph[id].type_check_first_pass()\n  File \"/Users/shantanu/dev/mypy/mypy/build.py\", line 3414, in type_check_first_pass\n    self.type_checker().check_first_pass(recurse_into_functions=recurse_into_functions)\n  File \"/Users/shantanu/dev/mypy/mypy/checker.py\", line 618, in check_first_pass\n    self.accept(d)\n  File \"/Users/shantanu/dev/mypy/mypy/checker.py\", line 765, in accept\n    stmt.accept(self)\n  File \"/Users/shantanu/dev/mypy/mypy/nodes.py\", line 1159, in accept\n    return visitor.visit_func_def(self)\n  File \"/Users/shantanu/dev/mypy/mypy/checker.py\", line 1332, in visit_func_def\n    self.visit_func_def_impl(defn)\n  File \"/Users/shantanu/dev/mypy/mypy/checker.py\", line 1336, in visit_func_def_impl\n    self.check_func_item(defn, name=defn.name)\n  File \"/Users/shantanu/dev/mypy/mypy/checker.py\", line 1369, in check_func_item\n    self.check_func_def(defn, typ, name, allow_empty)\n  File \"/Users/shantanu/dev/mypy/mypy/checker.py\", line 1551, in check_func_def\n    self.accept(item.body)\n  File \"/Users/shantanu/dev/mypy/mypy/checker.py\", line 765, in accept\n    stmt.accept(self)\n  File \"/Users/shantanu/dev/mypy/mypy/nodes.py\", line 1816, in accept\n    return visitor.visit_block(self)\n  File \"/Users/shantanu/dev/mypy/mypy/checker.py\", line 3275, in visit_block\n    self.accept(s)\n  File \"/Users/shantanu/dev/mypy/mypy/checker.py\", line 765, in accept\n    stmt.accept(self)\n  File \"/Users/shantanu/dev/mypy/mypy/nodes.py\", line 1836, in accept\n    return visitor.visit_expression_stmt(self)\n  File \"/Users/shantanu/dev/mypy/mypy/checker.py\", line 5139, in visit_expression_stmt\n    expr_type = self.expr_checker.accept(s.expr, allow_none_return=True, always_allow_any=True)\n  File \"/Users/shantanu/dev/mypy/mypy/checkexpr.py\", line 6177, in accept\n    typ = node.accept(self)  # r-value type, when interpreted as a value expression\n  File \"/Users/shantanu/dev/mypy/mypy/nodes.py\", line 2439, in accept\n    return visitor.visit_name_expr(self)\n           ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^\n  File \"/Users/shantanu/dev/mypy/mypy/checkexpr.py\", line 350, in visit_name_expr\n    narrowed = self.narrow_type_from_binder(e, result)\n  File \"/Users/shantanu/dev/mypy/mypy/checkexpr.py\", line 6486, in narrow_type_from_binder\n    narrowed = narrow_declared_type(known_type, restriction)\n  File \"/Users/shantanu/dev/mypy/mypy/meet.py\", line 185, in narrow_declared_type\n    elif not is_overlapping_types(declared, narrowed):\n             ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^\n  File \"/Users/shantanu/dev/mypy/mypy/meet.py\", line 379, in is_overlapping_types\n    assert False, \"Unexpectedly encountered partial type\"\n           ^^^^^\nAssertionError: Unexpectedly encountered partial type\n```","author":{"url":"https://github.com/hauntsaninja","@type":"Person","name":"hauntsaninja"},"datePublished":"2026-05-07T00:00:51.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/21423/mypy/issues/21423"}