[Sema] SR-2327: cherry-pick the change from pull request 4286 for swift-3.0-branch

lib/Sema/TypeCheckStmt.cpp

@@ -765,10 +765,14 @@ class StmtChecker : public StmtVisitor<StmtChecker, Stmt*> {
 
       // If someone is using an unlabeled break inside of an 'if' or 'do'
       // statement, produce a more specific error.
-      if (S->getTargetName().empty() && !ActiveLabeledStmts.empty() &&
-          (isa<IfStmt>(ActiveLabeledStmts.back()) ||
-           isa<DoStmt>(ActiveLabeledStmts.back())))
+      if (S->getTargetName().empty() &&
+          std::any_of(ActiveLabeledStmts.rbegin(),
+                      ActiveLabeledStmts.rend(),
+                      [&](Stmt *S) -> bool {
+                        return isa<IfStmt>(S) || isa<DoStmt>(S);
+                      })) {
         diagid = diag::unlabeled_break_outside_loop;
+      }
 
       TC.diagnose(S->getLoc(), diagid);
       return nullptr;

test/stmt/statements.swift

@@ -467,6 +467,28 @@ func r25178926(_ a : Type) {
   }
 }
 
+do {
+  guard 1 == 2 else {
+    break // expected-error {{unlabeled 'break' is only allowed inside a loop or switch, a labeled break is required to exit an if or do}}
+  }
+}
+
+func fn(a: Int) {
+  guard a < 1 else {
+    break // expected-error {{'break' is only allowed inside a loop, if, do, or switch}}
+  }
+}
+
+func fn(x: Int) {
+  if x >= 0 {
+    guard x < 1 else {
+      guard x < 2 else {
+        break // expected-error {{unlabeled 'break' is only allowed inside a loop or switch, a labeled break is required to exit an if or do}}
+      }
+      return
+    }
+  }
+}
 
 
 // Errors in case syntax