Support type literals as compile-time constants.

sdk/lib/_internal/compiler/implementation/compile_time_constants.dart

Index: sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
diff --git a/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart b/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
index f52407efe8984acdb0f1380dae1ac8c7fbc027fb..975d4e510e16b9e3cf508dcee0246a52f3af35ec 100644
--- a/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
+++ b/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
@@ -28,7 +28,6 @@ class ConstantHandler extends CompilerTask {
   /** 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>(),
@@ -248,6 +247,7 @@ class CompileTimeConstantEvaluator extends Visitor {
   final ConstantSystem constantSystem;
   final TreeElements elements;
   final Compiler compiler;
+  bool enabledRuntimeTypeSupport = false;
 
   CompileTimeConstantEvaluator(this.constantSystem,
                                this.elements,
@@ -400,6 +400,25 @@ class CompileTimeConstantEvaluator extends Visitor {
     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];
@@ -418,6 +437,8 @@ class CompileTimeConstantEvaluator extends Visitor {
           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) {
@@ -427,6 +448,8 @@ class CompileTimeConstantEvaluator extends Visitor {
         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) {