Support type literals as compile-time constants.

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 10 matching lines @@
 
   /** Set of all registered compiled constants. */
   final Set<Constant> compiledConstants;
 
   /** The set of variable elements that are in the process of being computed. */
   final Set<VariableElement> pendingVariables;
 
   /** Caches the statics where the initial value cannot be eagerly compiled. */
   final Set<VariableElement> lazyStatics;
 
-
   ConstantHandler(Compiler compiler, this.constantSystem)
       : initialVariableValues = new Map<VariableElement, dynamic>(),
         compiledConstants = new Set<Constant>(),
         pendingVariables = new Set<VariableElement>(),
         lazyStatics = new Set<VariableElement>(),
         super(compiler);
   String get name => 'ConstantHandler';
 
   void registerCompileTimeConstant(Constant constant) {
     compiler.enqueuer.codegen.registerInstantiatedClass(
@@ skipping 199 matching lines @@
     }
     return initialValue;
   }
 }
 
 class CompileTimeConstantEvaluator extends Visitor {
   bool isEvaluatingConstant;
   final ConstantSystem constantSystem;
   final TreeElements elements;
   final Compiler compiler;
+  bool enabledRuntimeTypeSupport = false;
 
   CompileTimeConstantEvaluator(this.constantSystem,
                                this.elements,
                                this.compiler,
                                {bool isConst: false})
       : this.isEvaluatingConstant = isConst;
 
   Constant evaluate(Node node) {
     return node.accept(this);
   }
@@ skipping 132 matching lines @@
       }
       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);
   }
 
+  Constant makeTypeConstant(Element element) {
+    // If we use a type literal in a constant, the compile time constant
+    // emitter will generate a call to the runtime type cache helper, so we
+    // resolve it and put it into the codegen work list.
+    if (!enabledRuntimeTypeSupport) {

[ngeoffray, 2012/11/19 16:54:09]

Instead of having a helper, you can have an implementation Dart subclass with a
constructor. This will be consistent with how we handle map literals for
example. Also, it avoids making these mistakes of forgetting to put a helper
(the class of the CTC is always registered as being instantiated).

[karlklose, 2012/11/20 14:04:38]

As discussed offline, I'll leave that change for now, because rti with constants
is broken. I have filed http://code.google.com/p/dart/issues/detail?id=6827.

+      SourceString helperName = const SourceString('createRuntimeType');
+      Element helper = compiler.findHelper(helperName);
+      compiler.enqueuer.resolution.addToWorkList(helper);
+      compiler.enqueuer.codegen.addToWorkList(helper);
+      enabledRuntimeTypeSupport = true;
+    }
+
+    DartType elementType = element.computeType(compiler).asRaw();
+    DartType constantType = compiler.typeClass.computeType(compiler);
+    Constant constant = new TypeConstant(elementType, constantType);
+    compiler.constantHandler.registerCompileTimeConstant(constant);
+    return constant;
+  }
+
   // 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);
         compiler.constantHandler.registerCompileTimeConstant(constant);
         compiler.enqueuer.codegen.registerStaticUse(element);
         return constant;
       } else if (Elements.isStaticOrTopLevelField(element)) {
         Constant result;
         if (element.modifiers.isConst()) {
           result = compiler.compileConstant(element);
         } else if (element.modifiers.isFinal() && !isEvaluatingConstant) {
           result = compiler.compileVariable(element);
         }
         if (result != null) return result;
+      } else if (Elements.isClass(element) || Elements.isTypedef(element)) {

[ngeoffray, 2012/11/19 16:54:09]

Could you use element.impliesType instead?

[karlklose, 2012/11/20 14:04:38]

That is not the same because type variables imply types.

+        return makeTypeConstant(element);
       }
       return signalNotCompileTimeConstant(send);
     } else if (send.isCall) {
       if (identical(element, compiler.identicalFunction)
           && send.argumentCount() == 2) {
         Constant left = evaluate(send.argumentsNode.nodes.head);
         Constant right = evaluate(send.argumentsNode.nodes.tail.head);
         Constant result = constantSystem.identity.fold(left, right);
         if (result != null) return result;
+      } else if (Elements.isClass(element) || Elements.isTypedef(element)) {

[ngeoffray, 2012/11/19 16:54:09]

ditto

[karlklose, 2012/11/20 14:04:38]

ditto

+        return makeTypeConstant(element);
       }
       return signalNotCompileTimeConstant(send);
     } else if (send.isPrefix) {
       assert(send.isOperator);
       Constant receiverConstant = evaluate(send.receiver);
       if (receiverConstant == null) return null;
       Operator op = send.selector;
       Constant folded;
       switch (op.source.stringValue) {
         case "!":
@@ skipping 383 matching lines @@
             // Use the default value.
             fieldValue = compiler.compileConstant(field);
           }
           jsNewArguments.add(fieldValue);
         },
         includeBackendMembers: true,
         includeSuperMembers: true);
     return jsNewArguments;
   }
 }