Support unreachable code in blocks in analyzer2dart.

sdk/lib/_internal/compiler/implementation/cps_ir/cps_ir_builder.dart

 // Copyright (c) 2013, 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 dart2js.ir_builder;
 
 import '../constants/expressions.dart';
 import '../constants/values.dart' show PrimitiveConstantValue;
 import '../dart_backend/dart_backend.dart' show DartBackend;
 import '../dart_types.dart';
@@ skipping 579 matching lines @@
     //
     // Return without a subexpression is translated as if it were return null.
     assert(isOpen);
     if (value == null) {
       value = buildNullLiteral();
     }
     add(new ir.InvokeContinuation(state.returnContinuation, [value]));
     _current = null;
   }
 
+  /// Create a blocks of [statements] by applying [build] to all reachable
+  /// statements.
+  // TODO(johnniwinther): Type [statements] as `Iterable` when `NodeList` uses
+  // `List` instead of `Link`.
+  void buildBlock(var statements, build(statement)) {
+    // Build(Block(stamements), C) = C'
+    //   where C' = statements.fold(Build, C)
+    assert(isOpen);
+    for (var statement in statements) {
+      build(statement);
+      if (!isOpen) return;
+    }
+  }
+
+
   // Build(BreakStatement L, C) = C[InvokeContinuation(...)]
   //
   // The continuation and arguments are filled in later after translating
   // the body containing the break.
   bool buildBreak(JumpTarget target) {
     return buildJumpInternal(target, state.breakCollectors);
   }
 
   // Build(ContinueStatement L, C) = C[InvokeContinuation(...)]
   //
@@ skipping 231 matching lines @@
     index = 0;
     for (int i = 0; i < environment.length; ++i) {
       if (common[i] == null) {
         environment.index2value[i] = parameters[index++];
       }
     }
 
     return join;
   }
 }