Extend the mandatory unreachable diagnostic pass to cover naive infinite recursion. The algorithm used is roughly the one from Clang with Swift-specific modifications and some minor simplification...
+func a() { // expected-warning {{all paths through this function will call itself}} + a() +} + +func b(_ x : Int) { // expected-warning {{all paths through this function will call itself}} + if x != 0 { + b(x) + } else { + b(x+1) + } +}
