Handle setter without getter for compounds in SemanticSendVisitor

pkg/compiler/lib/src/resolution/access_semantics.dart

Index: pkg/compiler/lib/src/resolution/access_semantics.dart
diff --git a/pkg/compiler/lib/src/resolution/access_semantics.dart b/pkg/compiler/lib/src/resolution/access_semantics.dart
index 10800dd3fdab5cf42db04de04b18886a1de7f5a8..096ddd17faa36da03564fc417864655ba613ca69 100644
--- a/pkg/compiler/lib/src/resolution/access_semantics.dart
+++ b/pkg/compiler/lib/src/resolution/access_semantics.dart
@@ -307,6 +307,22 @@ class CompoundAccessSemantics extends AccessSemantics {
       : super._(AccessKind.COMPOUND);
 
   Element get element => setter;
+
+  String toString() {
+    StringBuffer sb = new StringBuffer();
+    sb.write('CompoundAccessSemantics[');
+    sb.write('kind=$compoundAccessKind');
+    if (getter != null) {
+      sb.write(',getter=');
+      sb.write('${getter}');
+    }
+    if (setter != null) {
+      sb.write(',setter=');
+      sb.write('${setter}');
+    }
+    sb.write(']');
+    return sb.toString();
+  }
 }
 
 /// Enum representing the different kinds of destinations which a constructor