Support for new catch syntax in dart2js

dart/lib/compiler/implementation/ssa/builder.dart

 // Copyright (c) 2012, 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.
 
 class Interceptors {
   Compiler compiler;
   Interceptors(Compiler this.compiler);
 
   SourceString mapOperatorToMethodName(Operator op) {
     String name = op.source.stringValue;
@@ skipping 3188 matching lines @@
       add(exception);
       HInstruction oldRethrowableException = rethrowableException;
       rethrowableException = exception;
 
       pushInvokeHelper1(interceptors.getExceptionUnwrapper(), exception);
       HInvokeStatic unwrappedException = pop();
       tryInstruction.exception = exception;
       Link<Node> link = node.catchBlocks.nodes;
 
       void pushCondition(CatchBlock catchBlock) {
-        VariableDefinitions declaration = catchBlock.formals.nodes.head;
-        HInstruction condition = null;
-        if (declaration.type == null) {
-          condition = graph.addConstantBool(true);
-          stack.add(condition);
-        } else {
-          Type type = elements.getType(declaration.type);
+        if (catchBlock.onKeyword != null) {
+          Type type = elements.getType(catchBlock.type);
           if (type == null) {
-            compiler.cancel('Catch with unresolved type', node: catchBlock);
+            compiler.cancel('On with unresolved type',
+                            node: catchBlock.type);
           }
-          condition = new HIs(type, unwrappedException, nullOk: true);
+          HInstruction condition = new HIs(type, unwrappedException);
           push(condition);
         }
+        else {
+          VariableDefinitions declaration = catchBlock.formals.nodes.head;
+          HInstruction condition = null;
+          if (declaration.type == null) {
+            condition = graph.addConstantBool(true);
+            stack.add(condition);
+          } else {
+            // TODO(aprelev@gmail.com): Once old catch syntax is removed
+            // "if" condition above and this "else" branch should be deleted as
+            // type of declared variable won't matter for the catch 
+            // condition
+            Type type = elements.getType(declaration.type);
+            if (type == null) {
+              compiler.cancel('Catch with unresolved type', node: catchBlock);
+            }
+            condition = new HIs(type, unwrappedException, nullOk: true);
+            push(condition);
+          }
+        }
       }
 
       void visitThen() {
         CatchBlock catchBlock = link.head;
         link = link.tail;
         localsHandler.updateLocal(elements[catchBlock.exception],
                                   unwrappedException);
         Node trace = catchBlock.trace;
         if (trace != null) {
           pushInvokeHelper1(interceptors.getTraceFromException(), exception);
@@ skipping 374 matching lines @@
           new HSubGraphBlockInformation(elseBranch.graph));
 
     HBasicBlock conditionStartBlock = conditionBranch.block;
     conditionStartBlock.setBlockFlow(info, joinBlock);
     SubGraph conditionGraph = conditionBranch.graph;
     HIf branch = conditionGraph.end.last;
     assert(branch is HIf);
     branch.blockInformation = conditionStartBlock.blockFlow;
   }
 }