Mypy plugin

[emmatyping]

This is a WIP.

Currently it fails with:

Traceback (most recent call last):
File "c:\python37\lib\runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "c:\python37\lib\runpy.py", line 85, in _run_code
exec(code, run_globals)
File "mypy\checkexpr.py", line 3645, in accept
File "mypy\nodes.py", line 1496, in accept
File "mypy\checkexpr.py", line 1914, in visit_member_expr
File "mypy\checkexpr.py", line 1932, in analyze_ordinary_member_access
File "mypy\checkmember.py", line 126, in analyze_member_access
File "mypy\checkmember.py", line 143, in _analyze_member_access
File "mypy\checkmember.py", line 225, in analyze_instance_member_access
File "mypy\checkmember.py", line 376, in analyze_member_var_access
File "mypy\checkmember.py", line 537, in analyze_var
File "mypy\maptype.py", line 20, in map_instance_to_supertype
AttributeError: attribute 'type_vars' of 'TypeInfo' undefined
test.py:6: : note: use --pdb to drop into pdb