C# 15 can tell the compiler: this hierarchy is complete.
Mark a class `closed` and a switch covering its direct subtypes needs no fallback. Add a subtype later and the compiler flags the switch.
https://t.co/lm2PIEEOF8 https://t.co/BriD4vKyfI
C# 15 can tell the compiler: this hierarchy is complete. Mark a class `closed` and a switch covering its direct subtypes needs no fallba…