Support type variables as expressions.

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

Index: sdk/lib/_internal/compiler/implementation/world.dart
diff --git a/sdk/lib/_internal/compiler/implementation/world.dart b/sdk/lib/_internal/compiler/implementation/world.dart
index 8b737bf3057520084a2c77f7a564c2258a17aff3..2dacc283c3180f545e51cbbaba393084be7f9fef 100644
--- a/sdk/lib/_internal/compiler/implementation/world.dart
+++ b/sdk/lib/_internal/compiler/implementation/world.dart
@@ -12,6 +12,10 @@ class World {
   final Map<ClassElement, Set<ClassElement>> rtiDependencies;
   final FullFunctionSet allFunctions;
 
+  // The set of classes that use one of their type variables as expressions
+  // to get the runtime type.
+  final Set<ClassElement> classesUsingVariableExpression;

[ngeoffray, 2013/03/11 10:24:06]

Isn't that just an rtiDependency? So could  you just call registerRtiDependency
instead of having another set?

[karlklose, 2013/03/12 09:05:02]

No, this class and its subclasses need RTI because the method creates a Dart
value from them. The dependency would be between the method being called and the
class, but we do not track that.

+
   // We keep track of subtype and subclass relationships in four
   // distinct sets to make class hierarchy analysis faster.
   final Map<ClassElement, Set<ClassElement>> subclasses =
@@ -30,6 +34,7 @@ class World {
         classesNeedingRti = new Set<ClassElement>(),
         rtiDependencies = new Map<ClassElement, Set<ClassElement>>(),
         allFunctions = new FullFunctionSet(compiler),
+        classesUsingVariableExpression = new Set<ClassElement>(),
         this.compiler = compiler;
 
   void populate() {
@@ -130,6 +135,9 @@ class World {
         potentiallyAddForRti(variable.enclosingElement);
       }
     });
+    // Add the classes that need RTI because they use a type variable as
+    // expression.
+    classesUsingVariableExpression.forEach(potentiallyAddForRti);
   }
 
   Iterable<ClassElement> commonSupertypesOf(ClassElement x, ClassElement y) {