Crash for tuple unpacking in assignment rhs

[opk12]

$  cat test.py 
a, b = *(1, 2)

$  mypy test.py --show-traceback
test.py:1: error: Can use starred expression only as assignment target
test.py:1: error: INTERNAL ERROR -- Please try using mypy master on Github:
https://mypy.rtfd.io/en/latest/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 0.770+dev.d54fc8e78a8dd5be3c97c1aa0da357e313113dec
Traceback (most recent call last):
  File "/venv_/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/venv_/lib64/python3.8/site-packages/mypy/__main__.py", line 8, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "/venv_/lib64/python3.8/site-packages/mypy/main.py", line 89, in main
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/venv_/lib64/python3.8/site-packages/mypy/build.py", line 180, in build
    result = _build(
  File "/venv_/lib64/python3.8/site-packages/mypy/build.py", line 252, in _build
    graph = dispatch(sources, manager, stdout)
  File "/venv_/lib64/python3.8/site-packages/mypy/build.py", line 2611, in dispatch
    process_graph(graph, manager)
  File "/venv_/lib64/python3.8/site-packages/mypy/build.py", line 2918, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/venv_/lib64/python3.8/site-packages/mypy/build.py", line 3016, in process_stale_scc
    graph[id].type_check_first_pass()
  File "/venv_/lib64/python3.8/site-packages/mypy/build.py", line 2107, in type_check_first_pass
    self.type_checker().check_first_pass()
  File "/venv_/lib64/python3.8/site-packages/mypy/checker.py", line 294, in check_first_pass
    self.accept(d)
  File "/venv_/lib64/python3.8/site-packages/mypy/checker.py", line 401, in accept
    stmt.accept(self)
  File "/venv_/lib64/python3.8/site-packages/mypy/nodes.py", line 1062, in accept
    return visitor.visit_assignment_stmt(self)
  File "/venv_/lib64/python3.8/site-packages/mypy/checker.py", line 2011, in visit_assignment_stmt
    self.check_assignment(s.lvalues[-1], s.rvalue, s.type is None, s.new_syntax)
  File "/venv_/lib64/python3.8/site-packages/mypy/checker.py", line 2049, in check_assignment
    self.check_assignment_to_multiple_lvalues(lvalue.items, rvalue, rvalue,
  File "/venv_/lib64/python3.8/site-packages/mypy/checker.py", line 2510, in check_assignment_to_multiple_lvalues
    self.check_multi_assignment(lvalues, rvalue, context, infer_lvalue_type)
  File "/venv_/lib64/python3.8/site-packages/mypy/checker.py", line 2557, in check_multi_assignment
    self.check_multi_assignment_from_iterable(lvalues, rvalue_type,
  File "/venv_/lib64/python3.8/site-packages/mypy/checker.py", line 2735, in check_multi_assignment_from_iterable
    if self.type_is_iterable(rvalue_type) and isinstance(rvalue_type, Instance):
  File "/venv_/lib64/python3.8/site-packages/mypy/checker.py", line 2728, in type_is_iterable
    return is_subtype(type, self.named_generic_type('typing.Iterable',
  File "/venv_/lib64/python3.8/site-packages/mypy/subtypes.py", line 93, in is_subtype
    return _is_subtype(left, right,
  File "/venv_/lib64/python3.8/site-packages/mypy/subtypes.py", line 135, in _is_subtype
    return left.accept(SubtypeVisitor(orig_right,
  File "/venv_/lib64/python3.8/site-packages/mypy/types.py", line 1676, in accept
    assert isinstance(visitor, SyntheticTypeVisitor)
AssertionError: 
test.py:1: : note: use --pdb to drop into pdb

Version: Python 3.8.2, mypy master, Fedora 32

[JukkaL]

This seems to be essentially a duplicate of #3825 (or another related case).