Using TypedDict in function triggers AssertionError during compilation

[twoertwein]

from typing import TypedDict

class Movie(TypedDict):
    name: str
    year: int

def test(dictionary: Movie) -> None:
    for key, value in dictionary.items():
        print(key, value)

with mypy 0.900 and python 3.9

$ mypyc typed_dict.py
Traceback (most recent call last):
  File "mypyc/irbuild/builder.py", line 169, in accept
  File "mypy/nodes.py", line 1140, in accept
  File "mypyc/irbuild/visitor.py", line 148, in visit_for_stmt
  File "mypyc/irbuild/statement.py", line 252, in transform_for_stmt
  File "mypyc/irbuild/for_helpers.py", line 60, in for_loop_helper
  File "mypyc/irbuild/for_helpers.py", line 387, in make_for_loop_generator
  File "mypyc/irbuild/builder.py", line 719, in get_dict_item_type
  File "mypyc/irbuild/builder.py", line 711, in get_dict_key_type
  File "mypyc/irbuild/builder.py", line 705, in get_dict_base_type
typed_dict.py:8: AssertionError: 

[bibajz]

Hello, I can confirm this error is still present on

Python 3.9.7
mypy 0.920+dev.d263a9698fb59d7a1ae0c7817ef53bb272c8d875

Here is the full traceback:

Traceback (most recent call last):
  File "build_dir/py_plus_c/build/setup.py", line 5, in <module>
    ext_modules=mypycify(['typed_dict.py'], opt_level="3"),
  File "build_dir/mypy/mypyc/build.py", line 485, in mypycify
    groups, group_cfilenames = mypyc_build(
  File "build_dir/mypy/mypyc/build.py", line 398, in mypyc_build
    group_cfiles, ops_text = generate_c(all_sources, options, groups, fscache,
  File "build_dir/mypy/mypyc/build.py", line 200, in generate_c
    modules, ctext = emitmodule.compile_modules_to_c(
  File "build_dir/mypy/mypyc/codegen/emitmodule.py", line 414, in compile_modules_to_c
    modules = compile_modules_to_ir(result, mapper, compiler_options, errors)
  File "build_dir/mypy/mypyc/codegen/emitmodule.py", line 258, in compile_modules_to_ir
    scc_ir = compile_scc_to_ir(trees, result, mapper, compiler_options, errors)
  File "build_dir/mypy/mypyc/codegen/emitmodule.py", line 209, in compile_scc_to_ir
    modules = build_ir(
  File "/usr/local/lib/python3.9/contextlib.py", line 79, in inner
    return func(*args, **kwds)
  File "build_dir/mypy/mypyc/irbuild/main.py", line 82, in build_ir
    transform_mypy_file(builder, module)
  File "build_dir/mypy/mypyc/irbuild/main.py", line 125, in transform_mypy_file
    builder.accept(node)
  File "build_dir/mypy/mypyc/irbuild/builder.py", line 175, in accept
    node.accept(self.visitor)
  File "build_dir/mypy/mypy/nodes.py", line 696, in accept
    return visitor.visit_func_def(self)
  File "build_dir/mypy/mypyc/irbuild/visitor.py", line 116, in visit_func_def
    transform_func_def(self.builder, fdef)
  File "build_dir/mypy/mypyc/irbuild/function.py", line 69, in transform_func_def
    func_ir, func_reg = gen_func_item(builder, fdef, fdef.name, builder.mapper.fdef_to_sig(fdef))
  File "build_dir/mypy/mypyc/irbuild/function.py", line 306, in gen_func_item
    builder.accept(fitem.body)
  File "build_dir/mypy/mypyc/irbuild/builder.py", line 175, in accept
    node.accept(self.visitor)
  File "build_dir/mypy/mypy/nodes.py", line 1024, in accept
    return visitor.visit_block(self)
  File "build_dir/mypy/mypyc/irbuild/visitor.py", line 125, in visit_block
    transform_block(self.builder, block)
  File "build_dir/mypy/mypyc/irbuild/statement.py", line 46, in transform_block
    builder.accept(stmt)
  File "build_dir/mypy/mypyc/irbuild/builder.py", line 175, in accept
    node.accept(self.visitor)
  File "build_dir/mypy/mypy/nodes.py", line 1150, in accept
    return visitor.visit_for_stmt(self)
  File "build_dir/mypy/mypyc/irbuild/visitor.py", line 148, in visit_for_stmt
    transform_for_stmt(self.builder, stmt)
  File "build_dir/mypy/mypyc/irbuild/statement.py", line 254, in transform_for_stmt
    for_loop_helper(builder, s.index, s.expr, body,
  File "build_dir/mypy/mypyc/irbuild/for_helpers.py", line 60, in for_loop_helper
    for_gen = make_for_loop_generator(builder, index, expr, body_block, normal_loop_exit, line)
  File "build_dir/mypy/mypyc/irbuild/for_helpers.py", line 389, in make_for_loop_generator
    target_type = builder.get_dict_item_type(expr.callee.expr)
  File "build_dir/mypy/mypyc/irbuild/builder.py", line 761, in get_dict_item_type
    key_type = self.get_dict_key_type(expr)
  File "build_dir/mypy/mypyc/irbuild/builder.py", line 753, in get_dict_key_type
    dict_base_type = self.get_dict_base_type(expr)
  File "build_dir/mypy/mypyc/irbuild/builder.py", line 747, in get_dict_base_type
    assert isinstance(target_type, Instance)
typed_dict.py:8: AssertionError: 

I have also noted that wrapping the dictionary variable with dict makes the compilation successful:

from typing import TypedDict

class Movie(TypedDict):
    name: str
    year: int

def test(dictionary: Movie) -> None:
    for key, value in dict(dictionary).items():
        print(key, value)