Comment by coderedart

Local reasoning is the foundation of everything formal (this includes type systems) and anyone in the type-system-design space would know that. Graydon Hoare (ex-rust dev) wrote a post about it too (which links to another great without-boat's post in the very first line): https://graydon2.dreamwidth.org/312681.html

The entire point of having a static-type-system, is to enable local reasoning. Otherwise, we would just do whole program analysis on JS instead of inventing typescript.