Start new design for interceptors and implement String.charCodeAt with it.

sdk/lib/_internal/compiler/implementation/compile_time_constants.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.
 
 part of dart2js;
 
 /**
  * The [ConstantHandler] keeps track of compile-time constants,
  * initializations of global and static fields, and default values of
  * optional parameters.
@@ skipping 321 matching lines @@
     DartType keysType = new InterfaceType(compiler.listClass);
     ListConstant keysList = new ListConstant(keysType, keys);
     compiler.constantHandler.registerCompileTimeConstant(keysList);
     SourceString className = hasProtoKey
                              ? MapConstant.DART_PROTO_CLASS
                              : MapConstant.DART_CLASS;
     ClassElement classElement = compiler.jsHelperLibrary.find(className);
     classElement.ensureResolved(compiler);
     // TODO(floitsch): copy over the generic type.
     DartType type = new InterfaceType(classElement);
-    compiler.enqueuer.codegen.registerInstantiatedClass(classElement);
+    registerInstantiatedClass(classElement);
     Constant constant = new MapConstant(type, keysList, values, protoValue);
     compiler.constantHandler.registerCompileTimeConstant(constant);
     return constant;
   }
 
   Constant visitLiteralNull(LiteralNull node) {
     return constantSystem.createNull();
   }
 
+  void registerInstantiatedClass(ClassElement element) {
+    compiler.enqueuer.codegen.registerInstantiatedClass(element);
+  }
+
+  void registerStringInstance() {
+    registerInstantiatedClass(compiler.stringClass);
+  }
+
   Constant visitLiteralString(LiteralString node) {
+    registerStringInstance();
     return constantSystem.createString(node.dartString, node);
   }
 
   Constant visitStringJuxtaposition(StringJuxtaposition node) {
     StringConstant left = evaluate(node.first);
     StringConstant right = evaluate(node.second);
     if (left == null || right == null) return null;
+    registerStringInstance();
     return constantSystem.createString(
         new DartString.concat(left.value, right.value), node);
   }
 
   Constant visitStringInterpolation(StringInterpolation node) {
     StringConstant initialString = evaluate(node.string);
     if (initialString == null) return null;
     DartString accumulator = initialString.value;
     for (StringInterpolationPart part in node.parts) {
       Constant expression = evaluate(part.expression);
       DartString expressionString;
       if (expression == null) {
         return signalNotCompileTimeConstant(part.expression);
       } else if (expression.isNum() || expression.isBool()) {
         PrimitiveConstant primitive = expression;
         expressionString = new DartString.literal(primitive.value.toString());
       } else if (expression.isString()) {
         PrimitiveConstant primitive = expression;
         expressionString = primitive.value;
       } else {
         return signalNotCompileTimeConstant(part.expression);
       }
       accumulator = new DartString.concat(accumulator, expressionString);
       StringConstant partString = evaluate(part.string);
       if (partString == null) return null;
       accumulator = new DartString.concat(accumulator, partString.value);
     };
+    registerStringInstance();
     return constantSystem.createString(accumulator, node);
   }
 
   // TODO(floitsch): provide better error-messages.
   Constant visitSend(Send send) {
     Element element = elements[send];
     if (send.isPropertyAccess) {
       if (Elements.isStaticOrTopLevelFunction(element)) {
         compiler.codegenWorld.staticFunctionsNeedingGetter.add(element);
         Constant constant = new FunctionConstant(element);
@@ skipping 412 matching lines @@
             // Use the default value.
             fieldValue = compiler.compileConstant(field);
           }
           jsNewArguments.add(fieldValue);
         },
         includeBackendMembers: true,
         includeSuperMembers: true);
     return jsNewArguments;
   }
 }