Implement nested switches and missing switch continue targets.

pkg/kernel/lib/verifier.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 library kernel.checks;
 
 import 'ast.dart';
 import 'transformations/flags.dart';
 
 void verifyProgram(Program program) {
   VerifyingVisitor.check(program);
@@ skipping 13 matching lines @@
     try {
       location = node?.location ?? context?.location;
     } catch (_) {
       // TODO(ahe): Fix the compiler instead.
     }
     if (location != null) {
       String file = location.file ?? "";
       return "$file:${location.line}:${location.column}: Verification error:"
           " $details";
     } else {
-      return "Verification error: $details\nContext: '$context'.\nNode: '$node'.";
+      return "Verification error: $details\n"
+          "Context: '$context'.\n"
+          "Node: '$node'.";
     }
   }
 }
 
 /// Checks that a kernel program is well-formed.
 ///
 /// This does not include any kind of type checking.
 class VerifyingVisitor extends RecursiveVisitor {
   final Set<Class> classes = new Set<Class>();
   final Set<TypeParameter> typeParameters = new Set<TypeParameter>();
@@ skipping 378 matching lines @@
       String name = argument.name;
       for (int j = 0; j < function.namedParameters.length; ++j) {
         if (function.namedParameters[j].name == name) continue namedLoop;
       }
       return false;
     }
     return true;
   }
 
   @override
+  visitContinueSwitchStatement(ContinueSwitchStatement node) {
+    if (node.target == null) {
+      problem(node, "No target.");
+    } else if (node.target.parent == null) {
+      problem(node, "Target has no parent.");
+    } else {
+      SwitchStatement statement = node.target.parent;
+      for (SwitchCase switchCase in statement.cases) {
+        if (switchCase == node.target) return;
+      }
+      problem(node, "Switch case isn't child of parent.");
+    }
+  }
+
+  @override
   defaultMemberReference(Member node) {
     if (node.transformerFlags & TransformerFlag.seenByVerifier == 0) {
       problem(
           node, "Dangling reference to '$node', parent is: '${node.parent}'.");
     }
   }
 
   @override
   visitClassReference(Class node) {
     if (!classes.contains(node)) {
@@ skipping 53 matching lines @@
     var oldParent = parent;
     parent = node;
     node.visitChildren(this);
     parent = oldParent;
   }
 }
 
 void checkInitializers(Constructor constructor) {
   // TODO(ahe): I'll add more here in other CLs.
 }