So that we can write

bool foo(int x) {  switch (x) {    case 1: return true;    case 2: return false;    default: stop("Don't know this x");  }}

without issuing a warning.

There is a "noreturn" attribute forGCC andclang, but there might be other solutions.EDIT:http://stackoverflow.com/a/25408952/946850 is a nice SO answer that features__builtin_unreachable().

Retidyverse/dplyr#1878 (comment), CC@hadley.