Merge pull request swiftlang#33730 from DougGregor/fallthrough-nested

Author: swift-ci

lib/Sema/TypeCheckStmt.cpp

@@ -725,12 +725,16 @@ class StmtChecker : public StmtVisitor<StmtChecker, Stmt*> {
 
   struct AddSwitchNest {
     StmtChecker &SC;
+    CaseStmt *OuterFallthroughSource;
     CaseStmt *OuterFallthroughDest;
-    AddSwitchNest(StmtChecker &SC) : SC(SC),
+    AddSwitchNest(StmtChecker &SC)
+      : SC(SC),
+        OuterFallthroughSource(SC.FallthroughSource),
         OuterFallthroughDest(SC.FallthroughDest) {
     }
 
     ~AddSwitchNest() {
+      SC.FallthroughSource = OuterFallthroughSource;
       SC.FallthroughDest = OuterFallthroughDest;
     }
   };

test/SILGen/switch_fallthrough.swift

@@ -165,3 +165,20 @@ func test5() {
   e()
 }
 
+// rdar://problem/67704651 - crash due to nested fallthrough
+func testNestedFallthrough(x: (Int, String), y: (Int, Int)) {
+  switch x {
+  case (17, let s):
+    switch y {
+    case (42, let i):
+      print("the answer")
+    default:
+      print("nope")
+    }
+    fallthrough
+  case (42, let s):
+    print("42 and \(s)")
+  default:
+    print("done")
+  }
+}