Fix Rasta to correctly identify added break targets in switch statements.

pkg/compiler/lib/src/kernel/kernel_visitor.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.md file.
 
 import 'package:kernel/ast.dart' as ir;
 import 'package:kernel/frontend/accessors.dart'
     show
         Accessor,
         IndexAccessor,
         NullAwarePropertyAccessor,
@@ skipping 382 matching lines @@
 
   ir.LabeledStatement getContinueTarget(JumpTarget target) {
     return continueTargets.putIfAbsent(
         target, () => new ir.LabeledStatement(null));
   }
 
   ir.SwitchCase getContinueSwitchTarget(JumpTarget target) {
     return continueSwitchTargets[target];
   }
 
+  /// The optional positional parameter isBreakTarget can be added in cases
+  /// where a break statement was added but the element model and underlying
+  /// JumpTargets don't know about it.
   ir.Statement buildBreakTarget(
-      ir.Statement statement, Node node, JumpTarget jumpTarget) {
+      ir.Statement statement, Node node, JumpTarget jumpTarget,
+      [bool isBreakTarget]) {
     assert(node.isValidBreakTarget());
     assert(jumpTarget == elements.getTargetDefinition(node));
     associateNode(statement, node);
-    if (jumpTarget != null && jumpTarget.isBreakTarget) {
+    if (jumpTarget != null && (jumpTarget.isBreakTarget || isBreakTarget)) {
       ir.LabeledStatement breakTarget = getBreakTarget(jumpTarget);
       breakTarget.body = statement;
       statement.parent = breakTarget;
       return breakTarget;
     } else {
       return statement;
     }
   }
 
   ir.Statement buildContinueTarget(
@@ skipping 585 matching lines @@
     return !(node is ir.BreakStatement ||
         node is ir.ReturnStatement ||
         node is ir.ContinueSwitchStatement ||
         (node is ir.ExpressionStatement && node.expression is ir.Throw));
   }
 
   @override
   ir.Statement visitSwitchStatement(SwitchStatement node) {
     ir.Expression expression = visitForValue(node.expression);
     List<ir.SwitchCase> cases = <ir.SwitchCase>[];
+    bool switchIsBreakTarget = elements.getTargetDefinition(node).isBreakTarget;
     for (SwitchCase caseNode in node.cases.nodes) {
       cases.add(caseNode.accept(this));
       JumpTarget jumpTarget = elements.getTargetDefinition(caseNode);
       if (jumpTarget != null) {
         assert(jumpTarget.isContinueTarget);
         assert(!continueSwitchTargets.containsKey(jumpTarget));
         continueSwitchTargets[jumpTarget] = cases.last;
       }
     }
 
@@ skipping 12 matching lines @@
       for (Statement statement in caseNode.statements.nodes) {
         if (buildStatement(statement, statements)) {
           hasVariableDeclaration = true;
         }
       }
       if (statements.isEmpty || fallsThrough(statements.last)) {
         if (isLastCase) {
           if (!caseNode.isDefaultCase) {
             statements.add(new ir.BreakStatement(
                 getBreakTarget(elements.getTargetDefinition(node))));
+            // Because we "helpfully" add a break here, in the underlying
+            // element model the jump target doesn't actually know it's a break
+            // target, so we have to pass that information.
+            switchIsBreakTarget = true;
           }
         } else {
           statements.add(new ir.ExpressionStatement(new ir.Throw(
               new ir.ConstructorInvocation(
                   kernel.getFallThroughErrorConstructor(),
                   new ir.Arguments.empty()))));
         }
       }
       ir.Statement body = new ir.Block(statements);
       irCase.body = body;
       body.parent = irCase;
     }
     assert(!casesIterator.moveNext());
 
     return buildBreakTarget(new ir.SwitchStatement(expression, cases), node,
-        elements.getTargetDefinition(node));
+        elements.getTargetDefinition(node), switchIsBreakTarget);
   }
 
   @override
   ir.Statement visitSyncForIn(SyncForIn node) {
     return buildForIn(node, isAsync: false);
   }
 
   @override
   ir.Throw visitThrow(Throw node) {
     return new ir.Throw(visitForValue(node?.expression));
@@ skipping 1785 matching lines @@
       : this(null, true, node, initializers);
 
   accept(ir.Visitor v) => throw "unsupported";
 
   visitChildren(ir.Visitor v) => throw "unsupported";
 
   String toString() {
     return "IrFunction($kind, $isConstructor, $node, $initializers)";
   }
 }