[NFC] LifetimeCompletion: operator<<(boundary).

Author: nate-chandler

include/swift/SIL/OSSALifetimeCompletion.h

@@ -172,4 +172,18 @@ class UnreachableLifetimeCompletion {
 
 } // namespace swift
 
+inline llvm::raw_ostream &
+operator<<(llvm::raw_ostream &OS,
+           const swift::OSSALifetimeCompletion::Boundary &boundary) {
+  switch (boundary) {
+  case swift::OSSALifetimeCompletion::Boundary::Availability:
+    OS << "availability";
+    break;
+  case swift::OSSALifetimeCompletion::Boundary::Liveness:
+    OS << "liveness";
+    break;
+  }
+  return OS;
+}
+
 #endif