# Buggy code
def serialize(self) -> JsonDict:
    return {
        "name": self.name,
        "is_in_init": self.is_in_init,
        "is_init_var": self.is_init_var,
        "has_default": self.has_default,
        "line": self.line,
        "column": self.column,
    }


# Traceback (AssertionError)
bug.py:11: error: INTERNAL ERROR -- please report a bug at https://github.com/python/mypy/issues version: 0.701
Traceback (most recent call last):
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/bin/mypy", line 10, in <module>
sys.exit(console_entry())
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/__main__.py", line 7, in console_entry
main(None)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/main.py", line 84, in main
res = build.build(sources, options, None, flush_errors, fscache)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/build.py", line 163, in build
result = _build(sources, options, alt_lib_path, flush_errors, fscache)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/build.py", line 218, in _build
graph = dispatch(sources, manager)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/build.py", line 2461, in dispatch
process_graph(graph, manager)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/build.py", line 2761, in process_graph
process_stale_scc(graph, scc, manager)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/build.py", line 2862, in process_stale_scc
graph[id].semantic_analysis()
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/build.py", line 1997, in semantic_analysis
self.manager.semantic_analyzer.visit_file(self.tree, self.xpath, self.options, patches)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/semanal.py", line 309, in visit_file
self.accept(d)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/semanal.py", line 3791, in accept
node.accept(self)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/nodes.py", line 896, in accept
return visitor.visit_class_def(self)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/semanal.py", line 807, in visit_class_def
self.analyze_class(defn)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/semanal.py", line 825, in analyze_class
self.analyze_class_body_common(defn)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/semanal.py", line 833, in analyze_class_body_common
self.apply_class_plugin_hooks(defn)
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/semanal.py", line 895, in apply_class_plugin_hooks
hook(ClassDefContext(defn, decorator, self))
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/plugins/dataclasses.py", line 330, in dataclass_class_maker_callback
transformer.transform()
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/plugins/dataclasses.py", line 100, in transform
return_type=NoneTyp(),
File "/Users/ezyang/Dev/oss/dl-hmc-calc-env/lib/python3.7/site-packages/mypy/plugins/common.py", line 97, in add_method
assert arg.type_annotation, 'All arguments must be fully typed.'
AssertionError: All arguments must be fully typed.
bug.py:11: : note: use --pdb to drop into pdb

# Fixed code
def serialize(self) -> JsonDict:
    assert self.type
    return {
        "name": self.name,
        "is_in_init": self.is_in_init,
        "is_init_var": self.is_init_var,
        "has_default": self.has_default,
        "line": self.line,
        "column": self.column,
        "type": self.type.serialize(),
    }