Implement type argument access and reification of runtime types.

pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart

 // Copyright (c) 2014, 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 tree_ir_builder;
 
 import '../dart2jslib.dart' as dart2js;
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../cps_ir/cps_ir_nodes.dart' as cps_ir;
@@ skipping 104 matching lines @@
     return variables[primitive.registerIndex];
   }
 
   /// Obtains a reference to the tree Variable corresponding to the IR primitive
   /// referred to by [reference].
   /// This increments the reference count for the given variable, so the
   /// returned expression must be used in the tree.
   Expression getVariableReference(cps_ir.Reference reference) {
     Variable variable = getVariable(reference.definition);
     if (variable == null) {
+      // Note: this may fail because you forgot to implement a visit-function
+      // in the RegisterAllocator.
       internalError(
           CURRENT_ELEMENT_SPANNABLE,
           "Reference to ${reference.definition} has no register");
     }
     ++variable.readCount;
     return variable;
   }
 
   ExecutableDefinition build(cps_ir.ExecutableDefinition node) {
     if (node is cps_ir.FieldDefinition) {
@@ skipping 480 matching lines @@
   Expression visitContinuation(cps_ir.Continuation node) {
     // Until continuations with multiple uses are supported, they are not
     // visited.
     internalError(CURRENT_ELEMENT_SPANNABLE, 'Unexpected IR node: $node.');
     return null;
   }
 
   Expression visitIsTrue(cps_ir.IsTrue node) {
     return getVariableReference(node.value);
   }
+
+  Expression visitReifyRuntimeType(cps_ir.ReifyRuntimeType node) {
+    return new ReifyRuntimeType(getVariableReference(node.value));
+  }
+
+  Expression visitReadTypeVariable(cps_ir.ReadTypeVariable node) {
+    return new ReadTypeVariable(node.variable, node.context,
+                                getVariableReference(node.target));
+  }
 }
-