Constant folding of indexers

pkg/compiler/lib/src/types/abstract_value_domain.dart

Index: pkg/compiler/lib/src/types/abstract_value_domain.dart
diff --git a/pkg/compiler/lib/src/types/abstract_value_domain.dart b/pkg/compiler/lib/src/types/abstract_value_domain.dart
index 14c9939a9d1f0207ebb7a51b62c5f2b510fa0277..6512c5aa300f8f75149d9d23a68e18d7704e6830 100644
--- a/pkg/compiler/lib/src/types/abstract_value_domain.dart
+++ b/pkg/compiler/lib/src/types/abstract_value_domain.dart
@@ -161,4 +161,9 @@ abstract class AbstractValueDomain {
 
   /// The length property of [value], or `null` if unknown.
   int getContainerLength(AbstractValue value);
-}
+
+  /// Returns the type of the entry of [container] at a given index.
+  /// Returns `null` if unknown.
+  AbstractValue indexWithConstant(AbstractValue container,
+                                  ConstantValue indexValue);
+}