"absolute" is a bit of a funny qualifier to use here, given the many soundness holes in TS. For example (included with --strict): https://www.typescriptlang.o

"absolute" is a bit of a funny qualifier to use here, given the many soundness holes in TS. For example (included with --strict): https://www.typescriptlang.org/play/#src=class%20Base%20%7B%0D%0A%20%20f(x%3A%20string%20%7C%20null)%20%7B%20%7D%0D%0A%7D%0D%0Aclass%20Derived%20extends%20Base%20%7B%0D%0A%20%20f(x%3A%20string)%20%7B%20x.charAt(3)%3B%20%7D%0D%0A%7D%0D%0Alet%20b%3A%20Base%20%3D%20new%20Derived()%3B%0D%0Ab.f(null)%3B https://www.typescriptlang.org/play/#src=class%20Base%20%7B%... (I like TS, I just don't think it fully solves this problem!)