mypy crashes if collections import is removed from typing.pyi

Bug Report

Noticed during python/typeshed#11238: When removing the (now unnecessary) collections import from stdlib/typing.pyi, mypy 1.8.0 will crash with the following traceback:

Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "mypy/semanal.py", line 6539, in accept
  File "mypy/nodes.py", line 1310, in accept
  File "mypy/semanal.py", line 2889, in visit_assignment_stmt
  File "mypy/semanal.py", line 3393, in process_type_annotation
  File "mypy/semanal.py", line 6690, in anal_type
  File "mypy/types.py", line 955, in accept
  File "mypy/typeanal.py", line 259, in visit_unbound_type
  File "mypy/typeanal.py", line 399, in visit_unbound_type_nonoptional
  File "mypy/typeanal.py", line 6[24](https://github.com/python/typeshed/actions/runs/7411345628/job/20165674610?pr=11238#step:5:25), in try_analyze_special_unbound_type
  File "mypy/typeanal.py", line 1470, in analyze_literal_type
  File "mypy/typeanal.py", line 1484, in analyze_literal_param
  File "mypy/typeanal.py", line 1738, in named_type
  File "mypy/typeanal.py", line [25](https://github.com/python/typeshed/actions/runs/7411345628/job/20165674610?pr=11238#step:5:26)6, in lookup_fully_qualified
  File "mypy/semanal.py", line 5852, in lookup_fully_qualified
AssertionError: builtins.str

To Reproduce

Check out typeshed, install mypy, remove the collections import from typing.pyi and run ./tests/typecheck_typeshed.py, which will call mypy and include the traceback.

Your Environment

Python 3.11.6, mypy 1.8.0

typeshed's stdlib/typing.pyi から collections import を削除してクラッシュを再現し、その後 ./tests/typecheck_typeshed.py を実行します。mypy/typeanal.py と mypy/semanal.py の traceback のパス、特に analyze_literal_type と lookup_fully_qualified から調査を始めます。typeshed のチェックが builtins.str に対する AssertionError なしで完了すれば完了です。