Unlike the OP's file, there's a rather substantial test suite and massive corpus of TypeScript code to work with, so at the very least, you'd have some grumpy people knocking on your door if you did something that negatively impacted the greater ecosystem.
Some documentation from Orta Therox on the checker:
Some documentation from Orta Therox on the checker:
https://github.com/microsoft/TypeScript-Compiler-Notes/blob/...