dart2js CPS: implement special handling of the Symbol constructor.

pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.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_task;
 
 import '../closure.dart' as closure;
 import '../common.dart';
 import '../common/names.dart' show
     Names,
@@ skipping 2113 matching lines @@
       ConstructorElement current = constructor;
       while (current.isRedirectingFactory) {
         var prefix = current.redirectionDeferredPrefix;
         if (prefix != null) buildCheckDeferredIsLoaded(prefix, send);
         current = current.immediateRedirectionTarget;
       }
     }
 
     List<ir.Primitive> arguments = argumentsNode.nodes.mapToList(visit);
     // Use default values from the effective target, not the immediate target.
-    ConstructorElement target = constructor.implementation;
+    ConstructorElement target;
+    if (constructor == compiler.symbolConstructor) {
+      // The Symbol constructor should perform validation of its argument
+      // which is not expressible as a Dart const constructor.  Instead, the
+      // libraries contain a dummy const constructor implementation that
+      // doesn't perform validation and the compiler compiles a call to
+      // (non-const) Symbol.validated when it sees new Symbol(...).
+      target = compiler.symbolValidatedConstructor;
+    } else {
+      target = constructor.implementation;
+    }
     while (target.isRedirectingFactory && !target.isCyclicRedirection) {
       target = target.effectiveTarget.implementation;
     }
 
     callStructure = normalizeStaticArguments(callStructure, target, arguments);
     TypeMask allocationSiteType;
 
     if (Elements.isFixedListConstructorCall(constructor, send, compiler) ||
         Elements.isGrowableListConstructorCall(constructor, send, compiler) ||
         Elements.isFilledListConstructorCall(constructor, send, compiler) ||
@@ skipping 1678 matching lines @@
   }
 
   Element get closureConverter {
     return _backend.helpers.closureConverter;
   }
 
   void addNativeMethod(FunctionElement function) {
     _backend.emitter.nativeEmitter.nativeMethods.add(function);
   }
 }