Implement type checking raise from
New test cases for raise from type checking
Cast super_type from Instance down to Type
Add more raise from statement test cases
Remove unused class in fixtures/exception.py
Semantic analyze from_expr of RaiseStmt
Add raise from type checking
Add type_check_raise() function and remove duplicate code
Change type to Node
Merge pull request #463 from yczhu/raise-from

Implement raise from type checking